Stephen wrote:

I understand that Zircon stud detectors are recommended by this group.
I've looked at the Zircon web site and see they sell two types: edge
finders and centre finders. If you want to screw a shelf into a stud,
I guess the centre finder is best but if you are trying to avoid
cutting into a stud/joist, I suppose the edge variety is better?

What models do you use and do they work?

I've got one of these:
http://www.zircon.com/products/center_ms_i500.html
which I bought last summer in the US for only about 20 quid (the dollar
was only worth 50p then!)

This finds edges as well as centres... I expect all the centre-detectors
must do that, as presumably they find centres by interpolating between
edges? TBH I'm not sure of the advantage of a 'centre' detector; in
practice when I'm using it I sweep it across the wall and plot the
positions of the studs: you get a readout on the display which shows you
where they lie.

I really rate it, anyway: I've had two cheapo versions of these
detectors before which were complete rubbish.

David