Posted By Edward H Can you give some more information? Are you looking for a product that will allow someone to lean out of a fully open window [e.g. for cleaning the outside glass] in which case you are looking for a fall restraint harness and lanyard system [many suppliers] and properly installed and tested anchor points adjacent to the window on the inside. [Hilti offer a service]. If you are looking for products that will restrict the windows from opening wide enough to allow persons to fall/climb out then these are also common, [they are also marketed for the security benefit of stopping people from climbing in], however they will depend on the particular type of window so you will probably need to speak to a local window supplier.

Posted By Natalie Crawford Sorry I should have explained better this is for during the construction process, to prevent people working inside a property falling from unglazed window openings.

Posted By Ken Taylor Sounds like you need temporary edge protection if the widow openings are too low or persons are working at a higher level where they could fall through. I've seen various improvised arrangements on site with boards, brick-guards, scaffold tubes, folding barriers, etc but not come across a purpose-designed system in use.