This is a wall mounted tool holder for a Harbor Freight Miter Box. The box and saw are only $12 and this keeps them out of the way on my workbenches. The fit is just tight enough to snap it into place but loose enough that you can pull it off with one hand from the front.

The saw and miter box and for sale here: https://www.harborfreight.com/miter-box-with-saw-66562.html

If you would like to see or edit the original design, it is shared here: https://cad.onshape.com/documents/613fc9c3d8f3c0b5425c5655/w/6b3f755414172cc9c2c5f561/e/d671bb68ac7db72c75e459cb