The pool cover was always flying of, so a solution was needed. I found it on Thingiverse.com (link below)

Update:
I quickly realized that PLA was not the right material for this print, so I ordered PETG, this was the first time I did not print with this material.
After the first print and test on the pool, I discovered that the clip was not holding like I would have it to hold.

The pool is big and can catch lots of wind.

So, I started up Fusion 360 and create a new clip based on the model from Thingiverse.com by zorco.
This clip is thicker, little extra thickness in the small.

It is printed at 100% infill.
A new STL file can be found below.