Samsung have made repairs rather simple by using the same sized screw ever since I can remember, however on the S6, S6 Edge and S7 series phones the screws are slightly smaller and will cause issues if the incorrect screw is used.
S6 – S7 Series phones use a 3.2mm philips head screw
The old samsung’s (S2-S5 series) use a 3.8mm screw
If you happen to loose a screw (which for technicians is a twice daily occurrence) do no use the 3.8mm instead as this will happen:
I am surprised I did not loose the whole screen as Samsung LCD’s are very fragile and first sign an internal crack renders the whole screen useless. In this case I over screwed a 3.8mm screw and it went into the curve of the s6 edge LCD taking out about 20 pixels, and glitched with lines going across screen, I removed the screw and grinded it down to 3.2mm, which removed the glitch however pixels are still dead. No further issues with the screen after 1 month.