Hardware to make pinch sticks

Pinch sticks are a tool used to make sure that a box is square while being glued and drying.  The box can be a drawer, a cabinet carcass, a bookshelf, a picture frame, or anything else that needs to have equal diagonals.

The tool is formed from two sticks, two sliding sleeves, and two pointers.  Each stick has a pointer on one end, and the other end goes through the sleeves.  Both sticks go through both sleeves.  Each sleeve has a thumbscrew that can be turned to lock the sticks into position.  To measure a box,

1. Pick two opposite corners
2. Loosen thumbscrews
3. Set a pointer in each corner
4. Extend the sticks so each pointer touches exactly
5. Tighten thumbscrews 
6. Now switch corners to the other diagonal and measure with the sticks. 

If length is the same, you’re done. Otherwise rack the box to shorten the long diagonal, then repeat measurement.

For very long pieces, the system can be extended with two additional sleeves and an additional stick; see https://www.reddit.com/r/functionalprint/comments/13lx664/hardware_and_pointers_make_three_yardsti

The sleeve models are designed for US 1/4-20 hardware.  Each sleeve has a quarter-inch hole for the thumbscrew, and the inside has a hexagonal recess that holds the corresponding 7/16" hex nut.  Depending on your printer you may be able to press-fit the nuts into place, or you may need CA glue.

Both the sleeves and the pointers should be printable without supports, although the curved parts of the pointers will look ugly.  The sleeves don't take much force, so heavy infill is not necessary.