My Lee reloading press came with a red quantum tool bin to catch completed rounds as they come off the press. where I was able to mount it, larger rounds have a tendency to bounce out. I looked at the bin and saw the grooves for something to blank off the front, and finally found them online by searching for windows, well didn't want to pay what they wanted and they tend to come in a pack.. I only need 1, so rolled my own. The purpose is to provide a dam at the front of the toolbin so that the rounds don't bounce out. the particular bin is a quantum QUS210 http://www.quantumstorage.com/qus210

a second look shows that Lorenzo Gonzales did something similar back in 2017: https://www.thingiverse.com/thing:2219217

functionaldiyer did a similar design but both his and Lorenzo's are for akro bins: https://www.thingiverse.com/thing:2754493