Fits single hung vertical sliding windows constructed of vinyl, 350 Series by BetterBilt These locks mount on the check (or “meeting”) rails of single and double hung sash where their checkrails rest flush when closed Replacing loose-fitting, worn or missing sash locks can help restore and increase the safety and security of the home or office This model is a right-hand lock, and the left-hand lock is also available under the part number F 2625 Both the lock body and keeper have mounting holes that are spaced apart at 2-1/16 inch, on center