This is an underdesk mount for a tailor's clapper - used by sewists and quilters to keep seams open or closed.

This model was designed for the clapper sold by Cotton & Bourbon (https://www.cottonandbourbon.com/quilting-extras/clapper) and can be attached to the bottom of the desk using the screw holes or with double sided tape.

I have also included the source OpenScad files if you want to resize it.