A simple gauge for checking legal sizes of shellfish (Cornwall, UK). Lobster, edible/brown crab, spider crab, cockle (must not fit through the 2cm circle). See the attached PDF (IFCA-rules-for-recreational-shellfish.pdf) for which part of the creature to measure. Please familiarise yourself with all local bylaws and regulations before use.

Source OpenSCAD file and SVG (for sizes and text layers) included.