Sash jammers are a good additional security measure for UPVC windows and doors though are pretty useless unless securely fixed into the aluminium inner profile. Some UPVC doors and windows are purely hollow plastic and impossible to gain a solid fixing for sash jammers making them pretty useless as additional security.
A few tiny test holes will confirm what is inside the profile for fixing. Aluminium profile isn’t magnetic so cannot be determined in that way either.
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