I have a hollowcore internal door that I wish to fit a mortice lock to. The door has a "lock block" fitted on one side internally to take such a lock. I'm very confused about the position of this block. The door instructions state that the block is located "900mm from the bottom of the door on the marked side".
Now I know that I've got the right side as there is a arrow pointing to it on the top edge of the door. What I don't know is weather this 900mm is to the bottom edge of the lock block or is it the centre of the lock block. I don't want to drill the door without being certain. I've tried tapping the face of the door with a screwdriver handle to try to hear if it's hollow or not in the area, but I can't seem to distinguish the sound.
Is that 900mm likely to be the bottom edge of the block or the centre?
Togo, the door packaging states that the block is 320mm high and 80mm wide. It doesn't look central to me using the guidance of hc4361, but I'll have to measure it to check.
I don't recommend the "tapping to get hollow sound" method - I tried it and got it wrong. But at least I could then poke around through the hole to find where the block really was.