This is my take on a back up lid lock design for Packout model 48-22-8435. It is designed to press fit into the side of the handle unlike other designs that need a screw and a hole drilled through the handle so that way you can use it full time or if you just want to test it and see if you like it you can without drilling permanent holes in your handle. It's purpose is to be used as a backup latch to keep the lid from opening up and spilling everything inside in case you forget to close the factory latches. It is a very snug fit when putting the handles down because this box doesn't have as big of a gap on the sides as other boxes.

I would recommend to print this in ABS, ASA or at the very least PETG. I printed mine in PLA plus only because it will not be outside very much if ever so if that is the case PLA or PLA plus would be fine for this.