When you use screws with masonry, you have to drill a hole first. This hole will necessarily be a little big, and so you’ll have to pack the hole with a plug. Plugs are made of plastic, although you can use wood (you’ll see wood in some very old holes!). Like hoovers, one brand has lent its name to wall plugs, so you’ll come across Rawl plugs a lot.
There are various different plugs, and most will say for light, medium or heavy stuff. It’s quite important to get the right one. If you’re hanging a picture, you can use a little red plug. But if you’re putting up a bookshelf, you need to use a fat brown plug. Unless it’s plasterboard, when you need a plasterboard plug.
Packs of plugs will give you two numbers – the size of drill bit and the size of screw. The drill bit is in mm and is a masonry bit (photo to come). You can get away with a size smaller or a size bigger, depending on the wall. You may need a hammer to hit the plug home so that it is flush with the wall. Below will be photos of how to insert your plug.
The screw size is the diameter rather than the length. Obviously, you don’t want a screw that’s longer than the hole you’ve drilled…
Plasterboard is different from solid masonry (brick, stone, concrete). It’s about a cm thick and quite soft (it’s made from gypsum). Plasterboard plugs work by expanding behind the plasterboard, thus spreading the load on the hole. Some plasterboard plugs are metal or plastic screws. These don’t generally require a pre-drilled hole (if using plastic, go slow with the drill-driver, otherwise you’ll melt the plastic! I know. I’ve done it.) The screw thread gives a lot more surface connexion – just as a screw does as opposed to a nail.
Plasterboard fixings will work fine on masonry walls. Ordinary plugs will usually work on plasterboard, but if something heavy is to be suspended, it’s worth getting the right plugs!