No more nails is a proprietary gap filling adhesive in a tube from Unibond, that you apply using a sealant gun.

It bonds to most clean dry surfaces, and doesn't mind them being uneven, as long as they are sound.

The main problem in using it is part of its advantages: It is a rapid dry product.
I would suggest that before you go to stick something up, you offer it into place and ensure that it will fit first time, because once you have applied the glue, it starts to skin over , and will not bond if you fiddle around for long before putting into place.

This skin can be broken by using a twisting motion when putting the item in place, or just by mechanical pressure [otherwise known as 'squishing it in'].

If you are trying to fix a heavy item, you can use no more nails as a contact adhesive:
press your item into place to distribute the glue onto both surfaces, pull off briefly, then push back into place. This shortens the drying time, and means you need to support what you're sticking for less time.

If you find that you can't get on with the speed of its drying, there are equivalent products by many manufacturers that use water as a solvent: this gives a much longer open time, and stops your room filling up with nasty fumes.

If you find it a tad expensive, don't worry, as all the big stores and specialist suppliers now do their own equivalents:
[Screwfix's own brand is around £1.29 and just as good.] B&Q, Wickes et al all do it as an own label product that works, and of course is a lot cheaper because you don't have to pay for the advertising.

Update 7th April 2001- B&Q now offering a three pack of no more nails 4.97- a much better price if you need this much.