A screw is used to fasten paarts together with a nut, a standoff or directly into a threaded receptacle. We have here a pack-of-4 nickel plated screw with Philips hex cap. The thread size is M4, it fits other M4 screws/standoffs. The thread length is 10 mm. These screws come with attached washers. You can use an M4 hex wrench or a Philips screw driver to turn the screw.

M4 is also the standard size for VESA MIS-D mounting for monitors and flat displays.