Support for hot bed leveling with switch

I use this support to level the hot bed plate using Repetier Host. I put a switch at the end of the support connected with a battery and a led. Than I move the Z axis with Repetier Host until the led lights. I write the Z level (for example 0.3 mm). Than I do the same on the other corners of the plate and I adjust the plate level until I have the same measure (0.3 mm).