On Mon, 19 Jun 2006 18:42:16 +0100, Harry Bloomfield
wrote:

A ball joint would not be rigid enough, the joint angle would slip with
the lightest pressure. What is needed is one of those joints where it
locks with teeth giving a choice of several fixed angles. That would
need much less pressure on the joint bolt to make it stay where put.

Yes - a joint with teeth of some kind that lock together when a screw
is tighetened would be ideal.

BTW I chose my words badly when I said "infinitely adjustable" The
joint only actually needs to give adjustment from zero degrees to
about 15 degrees - however just about any angle within that range must
be possible; that's what I meant. I only need to change the angle in
one plane/direction; i.e., a universal joint is not required.

The type of joint used to give adjustable tilt to garden parasols is
the kind of thing I need - but it must be strong and hopefully
corrosion-proof, as it will be used under seawater.

Thanks to all for the responses so far.

Al D