Snaps on to T-post with 8mm threaded hole to mount a sign. PETG and ASA work well.
Use this screw:

https://www.amazon.com/dp/B08BJYG4GL/ref=cm_sw_em_r_mt_dp_840SR4DAD6T6M3WSAG9P?_encoding=UTF8&psc=1

M8-1.25x8mm 304 SS