How do you hang a picture if you don’t have a suitable picture-hook, the picture’s particularly heavy or the wall’s unsuitable for picture-hooks?
Easy. Drill a small hole into your wall, insert a Rawlplug or other type of wall plug. Put in a correctly sized screw. Hang your picture!
Hint: the larger and heavier the picture, the bigger the plug and screw should be. If it’s particularly heavy, and you’re fixing it to a stud partition wall, you may need to use a more substantial cavity fixing like a spring toggle (Screwfix Direct do a wide range of fixings).
DO NOT simply bang a nail into the wall. If the wall’s too solid (say, brick or breeze-block) you’re likely to waste a lot of nails that way. You’re also liable to worsen any weaknesses in the plaster (or, worse, the fabric of the wall). And it’s quite likely that at some stage the nail will slip out, very likely damaging the frame (and any glass pane) of your picture and possibly the picture itself.