Scrim tape should be used whenever two pieces of plasterboard have been joined. The scrim is applied and then the area should be plastered over using skimming plaster. If scrim is not used on the joints there is a high possibility that the joints will crack in the future.
Self adhesive scrim Tape
When Plasterboard has been used to board a wall there will always be gaps between the sheets, these gaps are weak points and when the plasterboard is plastered, these joints can often crack. To overcome this problem joints are taped with scrim which is a sticky fibrous tape, the tape itself is not really that sticky and only just sticks to the plasterboard. Once a coat of plaster has been applied though it will be impossible to remove.
Smooth the tape into the joints ensuring that it covers both sides of the joint as equally as possible. Then cut it to the correct length using a sharp knife.
Internal corners also need taping to prevent cracking, again ensure that the scrim covers both sides of the joint equally.
As soon as the scrim has been applied the joints can be plastered over.
Scrim tape should only be used on joints and internal corners, for external corners angle beading should be used- How to fit angle beading