3M Style Canvas Hook / Wedge

The 3M ones cost £2.80, these ones work out about 5p, so about 50x cheaper! :D

They only take about 20 minutes to print, quality isn't really an issue as you won't see it, and they'll be plenty strong enough.

It's designed for a slim canvas print (20mm slim frame from Snapfish), and Wilko adhesive strips, which are about 36mm x 16mm, it's easy enough to scale in Cura if you want something different.