Proper fasteners for heater control

Well thanks for all the info guys. Now Im not sure, I thought I had original stuff cause of what RRA posted, but now Im not sure; I was even able to get the nuts off of the studs just now without any damage to the studs. Now I wonder if I should drill/tap to the next size up machine screw rather than use the studs. And I agree, the parts manual is useless for this.