I want to add a stainless steel light switch to a dryline box and the instructions say that the switch must be earthed, the diagram shows it earthing to the earth terminal in the back box.

The dryline box doesn’t have an earth connector, which I don’t think is unusual but I’m now left wondering what to do with my light switch, will it be ok to connect the earth terminal of the circuit wiring to the light switch or will this give me an electric shock?

If you had a metal back box then you connect the switch earth and the box to the earth in the cable*. As you have a plastic box then just connect the switch earth to cable earth. Make sure it is sleeved. If there is no earth, which can happen with older wiring, then you can’t use that switch.

*technically cpc not earth but keeping it simple

The earth (yellow/green or sometimes just green) of the cable that appears into the dry lining box can safely be attached to the earth terminal of the metal switch.

Rich.

Thanks all.

Why is it important to sleeve the earth wire, is it to make sure its earthing properly?

to make sure its not contacting anything else in the box and being made live – mmmm earth fault…. – those can be annoying to find.