If the 'carved foam' technique is to be used for the bodywork, as will happen next here, foam blocking can also be used to simplify sheet GRP fabrications. Here, a foam block has been glued to the upper and lower sheets that form the rear light mounts (Ford Ka units). Later GRP can be laid onto it to form a very strong box that would be difficult to make from sheets
When flat sheets of flat GRP or with right angled edges as seen below are not enough, several sheets can be joined together with resin and glass laid into the joins to 'weld' the assembly together.
The assembly needs to be held together firmly enough to maintain the right shape while the strips of glass are laid up, but in a way that will not intrude on the finished part.
Sheets of GRP are normally joined up with the 'good' surfaces (facing the table when laid up) outboard and the rough surface is used for the jointing layup. To avoid resin running onto the good surfaces, that may be finished surfaces, lay a strip of masking tape along the join.
The surfaces that are to be laid up onto MUST be cut back to 'Grey' with all cured surfaces (Glossy) cut away. This ensures a good bond when resin is laid "Wet on Dry". (Work "Wet on Wet" if possible) 40 or 60 grit "production paper" is normally used for this