You can use a screw to bite into plastic. You can create a clearance hole to accommodate a bolt and a nut or even build in a nut trap. You can also heat-set threaded inserts. Which is the best?

Step 5: Insert the screw extractor ... or drill to turn the tool counterclockwise. As you turn the screw extractor, its threads will draw it in until it bites into the hole.

Heat-set inserts grant us proper screw threads in any thermoplastic. Simply heat them up, stake them into your part, let cool, and: voila–a screw thread that’s firmly embedded into our part.