For this restricted-opening windows project in Telford, opening checks, frame fitting and finishing are treated as one sequence. Perimeter Sealing leads the review, so we form a continuous weather-resistant seal around the external frame perimeter. We use restrictors and trims around restrictor type, opening angle, handle operation, frame fixing and user access, ensuring we configure restrictors where controlled opening forms part of the brief and coordinate internal or external trims with reveals, frame position and adjoining finishes, with perimeter sealing kept as the lead check for this restricted-opening windows scope. The last technical check is frame position; we set the new frame at a position that works with the reveals, sill and external finish, with perimeter sealing kept as the lead check for this restricted-opening windows scope. This supports windows that retain practical ventilation while limiting the opening range.