In reply to ramon marin martinez:
Plasterboard is no good, but there'll be wooden studs (ie: vertical 2x3" timbers) about 18" apart that'll be ok.
What I'd suggest is that you put a wooden board between your fingerboard and the wall. The board needs to be wide enough to match the width of your fingerboard, and long enough to reach between studs either side of it. (And if there's one in the middle, thats a bonus.)
First you need to find the studs. A stud detector is the easiest way, they cost about a tenner to buy if you can't borrow one. You can find the studs without but its tricky - a mixture of educated guesswork, tapping the wall and listening for changes in the sound and trial/error.
Once you found them, mark out where the board is going on the wall, and where your fingerboard is going on the wooden board. Its probably neatest (and strongest) to drill the board and use t-nuts & suitable screws (bolts) for your fingerboard.
Screw the board directly to the wall studs (with wood screws, something like 2.5" number 10s) - you'll need to drill pilot holes to avoid splitting the board. If the board spans 3 studs, you can leave off your fingerboard until its fixed to the wall, and then bolt it on.
hth
Sean
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