Linear reciprocative pseudogears
Basically intermeshing racks with angled teeth.
Not referring to the attack angle but to the angle relative to the tacks normal vector.
But unlike racks they are used like gears to …
– get transmission leverage rations (gear-up / gear-down)
– get the functionality of a mechanical differential
… thus "reciprocative (pseudo)gears".
(wiki-TODO: Add visual examples of use as gearing transmission and as differential.)
Usage as gears but all linear
Linear reciprocative transmission gearing
(wiki-TODO: Add a visual illustration. And OpenSCAD code?)
Reciprocative (pseudo)gear differentials

Alternate uses (not as gears)
multi part elongation by mutual interlocking
Making them coaxially intermesh (partial form closure) can be used to extend their length.
Slide-apart normal to their main axis is prevented by vdW force.
Or additionally due to placement into a guiding channel.
As tensioning element
They can be used as core chain in a ReChain frame system.