Omni Antenna rounding aid 15mm

I'm building an antenna for outdoors for TTN at 868MHz.

I found the following article:
https://www.thethingsnetwork.org/labs/story/homemade-outdoor-868mhz-antenna

In order to get the curves of the copper wire as clean as possible, I have devised an aid.
It fits for 2,5mm ^ 2 and 15mm diameter.

have fun