This is a small project I completed recently. Very simple really, requires no explanation, but I haven’t posted anything recently so I’ll explain it anyway. The only part that’s not obvious is what the heck this thing is, it’s a gauge for measuring scallops, not because I’m that bored but because there is a size limit on those babies. A word on material selection (it has no moving parts what else will I talk about) since the device is continuously exposed to seawater corrosion resistance is of paramount concern. Dimensional stability is also important since it is after all a measuring tool, so I went with 5/8 inch thick polyethylene (plastic cutting board from Walmart) it’s cut from a pattern made from Bristol board and traced onto the plastic with a permanent marker (the thin one I use for marking CDs) not much else will mark on polyethylene. This approach allows me to commit my precise measurements with a sharp pencil and X-Acto knife then trace the edge generously with the marker leaving a keen edge down the outside of the Mark to follow with the jigsaw. This also allows me to easily make two identical pieces and store the pattern against future need. The device features dual apertures in both 75 mm and 100 mm to serve in both my local scallop fishing zones and double ended attachment holes(you don’t really want to bring anything diving that you can attach.) I think it’s going to get clipped on to my pressure gauge, a nice handy place for it, but the truth is I tend to change my mind about such things after I try it.