Cut the enclosed c-shape from plywood to reinforce the edge of a torn out socket hole in a cavity wall. Suitable for holes of 68mm and mainly for single sockets.
Step 1: Cut C-shape
Find a Laser-cutting service or CNC-milling machine service or anything to cut the c-shape from solid plywood, around 5mm thick. Use the pdf or eps file. There also is a 10cm by 10cm square on these files to check the dimensions are transfered properly (Don't cut this shape).
You can of course alter them before with a vector graphics app like Inkscape.
Step 2: Insert and Fix
Insert the c-shape right behind the wall-board, clean if necessary. If position is obvious, fix the C with black drywall- (or any) screws right away.
In other cases, first attach a long screw to the C (yellowish in the picture, both the screw and the c-shape). Insert a cord through 2 holes of the internal junction box with the ends inside, so the box can be pulled out if necessary (red and orange in the picture, respectively). Prepare the orange junction box, that is, fold up the little overhanging plates on the screws to their initial positions. Put in the junction box holding the C shape. If appropriate, put it out again, still holding the C or leave it in the wall and mount it. Fix the C with black drywall- (or any) screws.
If not already done, mount the junction box, orange here. Make it's edge level with the wall. This can be tricky occasionally, but temporary screws through the plastic side of the box pressing against the wooden c-shape should help. Make the junction box horizontal or vertical, any of the 2.
Fill with filler or anything (white), this filler can also be bought in tubes. Let dry. The socket can be mounted again.
For electricity work, follow electricity work's guidelines. Cheers!