The most unobtrusive and cheapest way of securing the windows is to immobilise the sashes. Use a bolt to pass through both meeting rails. Close the window firmly and drill through the inner meeting rail until you reach the outer rail. Measure the depth of the bolt by marking the drill with tape. Then open the window and tap the two sections, which receive the bolt through the holes in the meeting rails.
If the bolt is too long for your particular frame saw its end to make it the required length. Then by closing the window, it should now be possible to insert the threaded bolt with the key until it fits snuggly and flush in the window frame.
Sash stops can be fitted on both sides of the window to allow for security plus ventilation. Drill a hole in the upper sash approximately 75mm (3inches) above the meeting rail. Screw the faceplate in place. If it is a close-fitting sash, you will need to recess the faceplate. If you need to open the window fully, push the bolts back with the key. This adds a useful feature, but is more obtrusive than other sash locks.
The keys should always be kept out of reach of the window, to deter burglars and also to stop children from opening the window wider.
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