I'd be a bit wary of using those for a shelf it is going to be loaded with books- I'd probably use these as they spread the load across the back of the board:
They are strong, but they require cutting a hole through the plasterboard that's wider thn the screw that then goes through it. The screw-in ones are rated at tens of kgs if I remember correctly, but judgement is obviously required. The best thing is to use a stud finder to erm find a stud and use a really long woodscrew to go clean through the plasterboard and into the wood.
They are strong, but they require cutting a hole through the plasterboard that's wider thn the screw that then goes through it. The screw-in ones are rated at tens of kgs if I remember correctly, but judgement is obviously required. The best thing is to use a stud finder to erm find a stud and use a really long woodscrew to go clean through the plasterboard and into the wood.