A sturdy gauge that shows you the right width to friction fit perpendicular slots on your projects.
Slots range from hairline to 7mm, in .25mm increments. It covers most thicknesses that can be cut with hobby lasers.
There is space in the center to log the settings and peak output used when you cut the gauge, so you can perfectly recreate the cut that made the gauge slot when you do your project.
Cut on a material you want to fit, and log the settings used down the center.
To find a fit, insert the material you want to friction fit into a slot that will take it. If the slot is too wide, move to a smaller slot until you find one that fits snugly.
On your project, make slots in the gauge material the width you found on the gauge to hold your interlocking material snugly. For a better fit, make gauges out of both materials and find two slots on the gauge that fit together.