Should be pretty self explanatory. You find these in ratchet wrenches and winches and anywhere else that you don’t want something to catastrophically spin out of control or if you want to move the input in the opposite direction without the output moving.
This was designed in Fusion 360 and the thingiverse number is here. I would recommend you print some extra stop pawls because that piece is an interference fit with the base and its better to have extras in case the fit needs to be better. Also some filing is necessary to fit your 3/8″ dowel. When you assemble it make sure you can rotate the crank 180 deg. There are two stops on the back which prevent you from rotating into the stop pawl. It is best to assemble everything, drill holes for the screws in the dowel, add the screws and flush cut the dowel.
Here’s a video: