The caliper is quite expensive, and the printed length isn’t long enough; plus, the spliced extensions aren’t precise enough, so I simply used a ruler as the standard,

while also accommodating the inch scale on the back of the ruler, allowing seamless switching between ruler and caliper modes.

The joints need to be sanded down; if they’re too loose, glue may be necessary. The tail-end stop is designed to be fairly tight, so it may need to be tapped into place.

The ruler is 26 mm wide and 1 mm thick.

A magnetic slot has been designed: the square slot accommodates 10×5×3 mm magnets (the magnets are slightly smaller than standard—since I designed the slot based on actual dimensions, if you purchase off-the-shelf magnets that conform strictly to standard sizes, they may not fit). These magnets must be secured with glue.

The round slot holds 5×3 mm magnets, which also require gluing for secure fixation.