Citation: Daniel Konstanski, The Secret Life of LEGO Bricks: The Inside Story of a Design Icon (Unbound, 2022). — p. 171.

Despite technically being new, the design of this anchoring brick closely mirrored the modified 2x4 Knud had come up with for the original LEGO wheel. Once again, holes were passed through each of a 2x4 brick’s walls. However, this time, instead of one hole per side, a bisecting tunnel was cast in between each pair of studs on all four walls; three on the long sides and one on the short faces.

The first Technic Brick from 1970 had holes on all sides. It was based on the custom 2x4 brick that early wheels with metal pins attached to.