These are the parts of the "ladder lock" that pulls and tightens straps and belts. Ladder locks are used in packing ,shoulder bags, etc. See the image...s in the gallery for how to attach the straps.
"20mm.stl" and "25mm.stl" are the standard versions, "20mmdivided.stl" and "25mmdivided.stl" are the divided versions. The divided version does not require re-sewing of the strap when replacing an existing ladder lock that has been broken.
"20mm" and "25mm" ( 1 inch ) correspond to the width of the strap.