if theyre snapped and sitting in the threads then you get a very small screwdriver, lube the threads then put the small screwdriver in the hole and spin it really quickly, hopefully the friction will twist it out, if it doesnt work, put PVA glue in there and put the screwdriver in there too, then twist it loose and it'll have hopefully molded to the threads and stuck to the remains of the bolt, then it will work as a screw head and twist it out. i hope you understand that
