If the top window keeps sliding down, the problem isn’t the sash lock. The problem is either that the sash weights aren’t heavy enough, or that the sash cord is too long and the weights are bottoming out in the pocket before the window gets to the top. Either problem is an easy repair.
If i was to fit one of these myself would I have to place them the other way around as to what this video shows to keep ones top window closed? Thank-You
You can break off a toothpick with a little wood glue in the hole, let dry and redrill the hole. I use epoxy putty to fill screw holes and then redrill. Either method will work.
Some rails have slid down over time, I know mine have. So the lock doesn't line up or even close on some. I put a little spacer on the sash rail that is sagging, normally the outer/upper sash to line up the lock and then install as you normally would.