I have this contraption with a floor plate that causes certain changes in a wall couple of blocks away (ie, firing pistons, etc). The floor plate is on a stone floor, and I wouldn't like to mess up the floor with redstone wire – all the wiring must be under the floor, and the floor must all be at one level.
Well, I fail to understand this thing: how to get the signal down from the block on which the floor plate was pushed, without any holes around the floor. Thing is, you can't put a redstone torch upside down. If you could, then I'd put it on the bottom of the floor block and pull the redstone wire to wherever I need, and all of that in the underfloor area, so nothing of that is visible from outside. But since you can not, it seems that there is no other way than have a how just besides the floor block with plate, where to put the redstone wire.
Best Answer
The pressure plate actually powers the block below it, so you can get the signal from below the block where the pressure plate is:
There is no need to have any holes on the floor.