Most Vesa mounts are supplied with a selection of screws to fit the backplate to the screen. With some screens, the supplied screws are too long, so the use of a junior hacksaw or a pair of bolt cutters is required.
The important thing is to make sure the screws aren`t too long, and you don`t screw them too far in so they damage the panel or and PCB inside the monitor. If in doubt, you should only need about 0.5cm of thread going into the monitor. I`d tighten one of the screws gently by hand first, to see how far it needs to go into the monitor. Many screens will have "stops", so it should be impossible to do damage, but you can`t always tell (especially if the screw diameter is small, so you can`t see the bottom of the hole).
