Help with ATX case

This is the first time I try putting a mainboard on a ATX case with “Snap-In” holes or mounts, anyways after I snap the needed one in I couldn’t find any instruction on which screw should be use. The tight thread hex seems to go in, but it doesn’t tighten, not sure if the loose thread hex, because it doesn’t really start “unless it’s met to be self thread” theres also pointed screws and screws that are no hex. Anyone got one of these type of Case and let me know the proper screw to use ?

hmm, i remember when i built my computer you had to have the screw perfectly perpendicular to the case so it would start or else it wouldn’t work. it shouldn’t really matter as long as the case stays in one place and the screw head isn’t touching anything metallic on the mobo.

Mobo ?