Mounting a solderless tie point
They may be intended to fit a mating plastic part. But you can still melt them if enough material sticks through the PCB. 

I had a similar issue with heat posts and simply turned an aluminum melting tool that fit a soldering iron end. It has concave hole to spread the post out and a stop to keep the thickness from being decreased too much. 

Worked a treat, and if you have a lathe handy it will almost take less time than it does to describe. 

Be sure to set the temperature no higher than it needs to be (maybe start off around 230°C) and keep the area well ventilated.