If the wall must be drilled through hole, and the length of the drill is not enough, then this operation can be performed in two stages: the one on the other side of the wall. Drill to the target point hole, put in a magnet or metal rod. Then using a compass find the point of drilling from the opposite side of the wall. The use of the magnet is preferable, as it will not allow the needle of the compass incorrectly indicate that the valve wall.
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