Overview
Identify the recess, trim profile and bottom sill before choosing a shutter frame. A window can combine several of these details. Compare the diagrams with the whole opening and with a side view of its edges.
Does my window have a recess?
Look at the opening from the side. If the window sits behind the room-side wall or trim, the space in front of it is the recess. Measure usable depth to the nearest handle, screen or other fitting; the distance to the glass can overstate the space available.
What is an architrave?
An architrave is the trim surrounding the opening. It covers the junction between wall and window and may have a flat, rounded or decorative face. Its shape determines where a Z-frame lip can sit or an outside frame can be securely fixed.
Bullnose architrave
Bullnose trim has a rounded outer edge and a relatively flat front face. Check that the chosen frame sits on that flat portion. The curved edge itself is not a level fixing surface.
Decorative architrave
Grooves, steps and raised mouldings identify a decorative architrave. An inside L-frame can leave this detail exposed. For an outside frame, locate a continuous flat band before taking measurements; the widest trim dimension may not describe a usable fixing surface.
Square architrave
Square architraves have straight edges and a simple flat face. They often suit either an overlapping Z-frame or a face-mounted L-frame, subject to recess clearance and a sound fixing surface.
Does my window have a sill?
A projecting bottom ledge is a sill. It can occur with or without an architrave. If it extends beyond the top and side surfaces, the shutter bottom usually finishes on top of it, so identify it before recording the drop.
