This page describes the engineering side of the DomiDo block: its geometry, the universal interlocking mechanism that defines it, the optional channel and reinforcement system, the manufacturing methods that suit its shape, and the technical performance that follows. DomiDo is built by Avvyland Limited (UK) and sells universal blocks and fasteners only; every construction shown on the platform is a user-generated design built from these blocks. The intellectual-property (IP) and patent strategy that surrounds the block is covered elsewhere in the compliance area; this page is engineering, not legal. The defining choice in the design is that every face of every block is an identical self-complementary mating surface, so any block can connect to any other block in any orientation, and the platform does not need a catalogue of corner, edge, top, or end variants to build arbitrary shapes.
The core invention is a self-complementary tetrahedral relief interlocking block system for construction-scale and modular building applications. The block is a parallelepiped — a cube or a rectangular box — whose faces carry a specifically defined interlocking surface relief built from tetrahedral protrusions and complementary tetrahedral recesses. The defining property is that identical mating faces interlock with each other: there is no male or female face distinction, no special block types for corners or ends, and no mandatory top or bottom orientation, so any block connects to any other block in any orientation.
This solves a set of recurring problems in modular building-block systems at the same time. The relief self-positions and aligns blocks during assembly, which reduces the need for jigs, fixtures, and skilled labour. Orientation independence eliminates the need to identify a privileged top or bottom and removes the need for special corner or end blocks. Constrained-space assembly remains possible because a final closing block can seat at a corner node where conventional relief patterns and insertion directions would otherwise block placement. Local reinforcement and adaptability arise from staggering, overlaps, and added connectors without forcing a fixed block orientation. Self-reproduction via formwork is possible because assembled blocks act as a mould cavity to cast new blocks that inherit the same mating surface relief. The same geometric interfaces also support a dual-use as an educational or play construction set at smaller scales.
The mating surface relief is the load-bearing differentiator of the block. It is not a generic symmetric pattern or a decorative texture — it is a rule-defined tetrahedral facet architecture generated by a deterministic geometric construction. The relief consists of tetrahedral protrusions that project outward from the face plane and tetrahedral complementary recesses that project inward; each tetrahedral element is formed from triangular planar side faces meeting at an apex, the protrusion vertex lies out of the base plane along the face normal, and the recess is its geometric inverse. The critical property is self-complementarity: the same relief pattern, applied to two separate block faces and brought together, interlocks because every protrusion on one face seats into a corresponding recess on the opposing identical face. This eliminates the male-female face distinction found in most interlocking block systems and is what makes the universal-block proposition possible.
The relief is generated by a deterministic construction on the square face of the block, and each step in that construction is load-bearing. Each mating surface is defined on a square base plane — the face of the parallelepiped — whose centre is fixed at the intersection of its diagonals; this centre is the sole rotational reference for the entire face pattern. The square face is then divided into four equal quadrants by partition lines drawn from the centre to the midpoints of each side, forming a plus-shape. Each quadrant is itself a square region with a fixed orientation relative to the centre and edges, and the partition is not arbitrary: it establishes the coordinate system in which the relief elements are placed.
Within each quadrant a paired protrusion and complementary recess — a dyad — is defined. Each quadrant contains exactly one tetrahedral protrusion extending outward from the base plane and one tetrahedral recess (complementary to the protrusion) extending inward, and the two are geometrically complementary so that they mate precisely. The base footprint of each tetrahedral element in the plane of the mating surface is a right triangle whose two legs (cathets) are oriented toward the centre of the square base plane; the hypotenuse lies along or adjacent to the outer boundary of the quadrant, so the acute geometry points inward toward the face centre while the broader hypotenuse edge faces the perimeter. The complementary recess has a right-triangle base aligned with the protrusion base to ensure precise mating.
The per-quadrant dyad is then replicated across the full face by ninety-degree rotational symmetry: the dyad in one quadrant is rotated about an axis normal to the base plane passing through the centre, in ninety-degree increments, and the rotation populates the remaining three quadrants with identical copies. The result is a four-part circular array with four tetrahedral protrusions, four tetrahedral recesses, and four-fold rotational symmetry about the face centre. When two blocks with the same face pattern come face-to-face, every protrusion on one face aligns with a corresponding recess on the other and every recess receives a corresponding protrusion, so the blocks seat into a deterministic final position with constrained lateral offset and relative rotation; the self-complementary property arises from the combination of the four-fold rotational symmetry and the specific pairing of protrusions and recesses within each quadrant. Because of that symmetry, a block can be placed without selecting a fixed orientation relative to predefined top, bottom, or side surfaces, a worker does not need to identify which face is up, and the same block can be rotated by ninety, one hundred and eighty, or two hundred and seventy degrees and still mate correctly — the mating surface self-positions the block on engagement.
The tetrahedral protrusions and complementary recesses have a defined taper angle measured relative to the base plane. The full operating range is from one degree to fifty degrees; the preferred range is from twenty to fifty degrees; the more preferred range is from forty to fifty degrees, with fifty degrees as the most preferred value. The taper angle determines the engagement depth, the draft compatibility for moulding, the surface area available for load transfer and shear resistance, and the manufacturing tolerance. A critical technical advantage of the tetrahedral geometry is that compatibility with standard moulding: all tetrahedral facets are planar faces — there are no curved, hooked, or re-entrant surfaces — and the tapered geometry shares a common withdrawal direction normal to the mating plane. Because there are no undercuts requiring side actions, collapsible cores, or other special mould mechanisms, the block can be produced by standard injection moulding for polymer, casting for concrete or gypsum, or three-dimensional printing without geometric complications. This differentiates the design from interlocking systems that require hooks, snap features, or elastic deformation for engagement.
The same mating-surface rule applies to several block configurations. The simplest is a cube where all six faces are identical squares and can carry the same mating surface relief; the cube has the highest degree of symmetry and is the most versatile for orientation-independent assembly. A rectangular parallelepiped — a brick shape with different length, width, and height dimensions — carries the mating surface relief on at least two faces, typically the opposing square faces, while other face pairs may have different dimensions and may or may not carry relief; this shape supports walls, columns, and structures with specific dimensional requirements. A composite multi-body configuration joins two or more parallelepiped sub-bodies permanently to form a single block that retains mating surfaces on its external faces, which supports L-shapes, T-shapes, and other complex geometries useful at corners and intersections.
The block body can include internal channels designed to receive connector or reinforcing elements — bolts, screws, pins, rods, ties, and rebar — and the channel features form a coherent system rather than a list of independent options. Channel axes can run perpendicular to a face, parallel to a face, or both; cross-sections include circles, ovals, polygons, and combinations of those shapes. Channels can be open along the outer surface, enclosed with at least one external outlet, mounted within a recess on the face, or open as through-holes on opposite faces. Longitudinal channels run the full block length, channels can appear on multiple faces, and stepped channel depths provide axial retention for connectors. Offset channels remain compatible with rotation, coaxial channels align with the normal to the mating surface base plane, and a single channel may combine straight and curved segments. Inside the channel, internal retaining relief grips connectors, a widened inlet provides a seat for reinforcement insertion, and a constriction acts as a retaining portion that prevents pull-out, while an end-face outlet supports through-structure reinforcement. Together these features enable multi-directional reinforcement, embedded inserts during manufacturing, and local strengthening without changing the block design.
Certain areas of a mating surface face are designated relief-free zones — flat areas without tetrahedral relief — and they exist because some operations need a flat surface. Adhesive application benefits from a flat surface that allows controlled adhesive spread; channels located on a mating face sit in a relief-free zone; a flat perimeter band absorbs manufacturing variation; and a smooth band provides a sealing surface for weather sealing or structural bonding.
The geometry is designed for standard moulding from the start. All relief features have draft-compatible taper angles, and the absence of re-entrant undercuts removes the need for side actions, collapsible cores, or lifters; a standard two-piece mould — core and cavity — with a single parting line at the base plane is sufficient, and the mould-withdrawal direction is normal to the mating surface plane. Standard thermoplastics including polypropylene (PP), acrylonitrile butadiene styrene (ABS), polyethylene (PE), and nylon are compatible, and cycle times suit high-volume production. The most innovative manufacturing concept is block-built formwork self-replication: a formwork structure is assembled from existing blocks with mating surface relief, the assembly creates an internal cavity whose walls include sections formed by the mating surfaces of the assembled blocks, a hardenable moulding mixture such as concrete, gypsum, or polymer concrete is introduced into the cavity, the material is cured or hardened (optionally with vibration for compaction), the formwork is disassembled cleanly because the tapered tetrahedral geometry releases without undercuts, the new block is demoulded with mating surfaces that reproduce the same relief because the cavity walls were formed by the mating surfaces of the formwork blocks, and the new block is then used as formwork to cast further blocks, perpetuating the relief geometry.
A number of additional manufacturing features support both moulding paths. Release-agent application before pouring eases demoulding, vibration compaction of the moulding mixture eliminates voids, forming inserts in the cavity create channels in the moulded block, decorative inserts in formwork produce decorative outer surfaces, smooth forming surfaces via inserts produce faces without mating relief where the build calls for it, and lightweight fillers reduce block mass without losing the relief geometry. Formwork blocks self-position via their mating surfaces, and the minimum formwork cavity is bounded by at least four blocks.
The block design is compatible with multiple material systems. Polymer thermoplastics serve toy-scale and light construction; concrete suits full construction-scale blocks; gypsum suits interior, lightweight, or fire-resistant applications; polymer concrete combines polymer binders with aggregate for enhanced properties; and lightweight fillers such as expanded polystyrene or hollow microspheres reduce block mass while maintaining structural integrity. The block material in the current product conformity notice is preliminary: ABS appears as a placeholder, and other resins — polypropylene, phenol-formaldehyde, polyamide, and recycled blends — remain open candidates without changing geometry. The trade-offs between candidate materials are discussed on the operations sustainability page rather than fixed at the block-design layer.
Block-design quality assurance is engineering quality assurance, separate from production quality assurance. It uses finite-element analysis (FEA) to validate structural performance under representative loads, interlocking-strength testing to measure engagement and disengagement force, shear strength at the joint, and cyclic-loading fatigue, accelerated weathering with a xenon-arc weatherometer to estimate outdoor lifespan, and third-party testing aligned with the relevant standards for the active use case. The same QA path applies to both moulded and cast blocks, and the relief geometry is verified after each material trial because taper, sharpness of vertices, and depth of recesses all depend on how a given material flows and cures.
The diagram traces the construction in the order the geometry rules apply it: the square face is fixed by the intersection of its diagonals, the face is partitioned into four equal quadrants by midpoint partitions, a per-quadrant dyad places one tetrahedral protrusion and one complementary recess on a right-triangle base, that dyad is rotated by ninety degrees three times to fill the face, and the resulting four-part circular array yields the four-fold (C4) symmetry that makes identical-face mating possible. The final node is the property that makes the rest of the platform feasible — identical-face mating with no male or female distinction and no mandatory orientation — which is what allows the gallery to host an arbitrary catalogue of user-generated designs built from a single universal block.