Zipper Mechanism: Slider Wedge & Cam (2D)

This 2D simulator lays a zipper flat and views it from above so its internal mechanism is fully visible: two tapes, each carrying a row of teeth, run side by side with their teeth offset from each other by exactly half a pitch. The slider — the part you actually grip — is modelled as a Y-shaped channel that narrows from two separate grooves down to a single point, the mouth, where a thin separator blade rides between the rows. Drag the pull tab (or the position slider) toward the closed side and each tape rides along the narrowing wall of its own groove, camming it sideways so the half-pitch offset lets every tooth slot past the centreline into the gap on the opposite row instead of colliding with it — that crossing-over is what actually locks them together. Drag the other way and the same wedge geometry runs in reverse, prying the interlocked teeth apart before the diverging grooves let each tape spring back out to its own side. It's the same mechanism as the site's 3D zipper-mechanism model, flattened into a cross-section so the cam action is easy to trace with your eye.