Fastener for BIG Shell Sandbox

The BIG Shell Sandbox seems to be relatively common in Germany for smaller kids.

So far we were using a rope to lock the sandbox (wind/weather/cats). When I printed a replacement splint for a Bobby Car, that model seemed to be a perfect fit for the sandbox as well. I can't say much about how well it works yet - we're just using it since a couple of days.

Do print in PETG (or ASA) for a better outside durability. You'll need 4 of them.

For reference, the hole diameter of the sandbox is ~13mm.