This is a knife guide for slicing bread.  I have it set up by default to slice 8 16 mm thick slices with a 3mm knife of a 140X140 mm loaf of bread.  

It's also fully parameterized, so if you want to change the bread size, slice thickness, number of slices in the guide, and even more properties of the guide itself like wall thickness, supports, knife thickness, etc you can remove the .txt from the .scad.txt and open it in OpenSCAD, or you can just customize it on thingiverse here: https://www.thingiverse.com/thing:4332708.  Their "open in customizer" functionality is kinda janky though so read the description there for how to get it to work.

Either way, this guide will help you get consistent bread slice thickness for all the bread you've been baking during the COVID lockdown!