Just as important as product selection is ensuring that you have appropriate fixing for your locks. Otherwise, the window lock finds no support in the wall or in the window frame.
Brand products tend to come with tested, universal fixings. Exceptions are indicated in the relevant fitting instructions.
What should you do if the subsurface is of poor quality?
On the initiative of the police, a standard has been established specifically for retrofitted locks: DIN 18104-1. Fixing materials are also covered by this standard.
"If the fixing conditions are poor (soft, hollow or porous subsurface, PVC windows with or without metal inserts and wooden windows) and/or the windows are vulnerable to tampering from the outside, extra locks and additional fixing materials (composite mortar, all-through screw fittings or fixing bolts) should be used. At least one lock per door or window should be lockable. If the frames themselves are too weak for effective fitting, it may be advisable to strengthen them."