This is a gridfinity insert I made for the excellent side tray that is compatible with the Harbor Freight Mini Toolbox that is (correctly) ridiculously popular. It is a slightly snug fit - you will likely have to press down gently to get it all the way in, and pull up gently to remove it if you decide you don't wish to use it any longer. I hope it works well for you!

Does NOT fit the original side tray, but rather the one below that has additional support.

Modified side tray with additional support: [https://makerworld.com/en/models/955811-harbor-freight-mini-tool-box-shelf](https://makerworld.com/en/models/955811-harbor-freight-mini-tool-box-shelf)