It depends on what it's made of, and its construction.

Ehr, do you mean bidet :0 or bird bath:)?
Quick setting cement applied with a trowel at the base will do. Be sure to have a bubble level across the top so you know the rim is horizontal. Smooth out the applied cement wearing goves of course. An alternative to this and maybe better would be to use epoxy putty which you can get at most hardware stores. Again, use gloves when applying.

I tried no nails but don't think its going to do the job, its concrete Rosie and its a bird bath Loose lol

Either concrete or what about some sort of sealant?

I might just phone the reclamation yard back and ask them Dan.

my hubby used bathroom silicon sealant to attach the bath to the pedestal.

I'm sure I have some of that in the shed Seaburn

There are lots of different styles of birdbath, Scots, which is why I asked. For example, no point in using concrete if only a small area of the bowl sits on the base as it will fail the second a large bird lands on it.

If you want proper advice, and only want to do the job once, post a photo. No-one can properly advise you without knowing what the birdbath looks like.

Yes that's what I'm talking about! Bathroom silicon! Did that with OURS and I used it to glue/bond the pipes to the waterfall! Never had a problem with it

Typical I just post a picture and go out to check the size of the bowl and it looks like no nails has done the job :) it's solid I honestly didn't think that would work! thanks for the help anyway guys.

I tried No Nails on one of my ornamental lights, it only lasted a day, one whack from Brynners tail and cherubs wings went flying across the patio without said cherub, back to the drawing board on that one, lol....

lol Lincs Sods Law eh! I've pushed and pulled it a little it's not budging, I'll keep testing it every day just encase, Knowing my luck it will fall and hit the slab.