Peg for weedmat, plastic sheet, etc.

A simple flat-top peg for pushing into the ground. I made a more serrated version (like a pine tree) that might work better.

Can be scaled 200% in Z axis to produce a more useful length. Double-point design intended for piercing plastic sheet. My CAD skills are limited, so I've included the files (from RS DesignSpark Mechanical) which you might like to improve.