Arch windows and specialty shapes

A half-round or eyebrow arch above a standard window can be covered three ways: a fixed sunburst or fan arch shade, a movable arch on a track, or shutters with a matched arch frame. Fixed arches are far cheaper and are usually the right call when the arch is high and decorative rather than a glare source. Movable arches cost significantly more and need clearance the photos will show you.

Three or more panels meeting at angles. The critical decisions are whether blinds sit inside each individual frame or span the bay, and how the corners are handled so adjacent blinds don't collide when raised. Bow windows with shallow angles usually take individual inside-mount shades; sharp 45° bays often look best with shutters and mitred frames.

Gravity works against every skylight covering, so they need side channels or a tensioned cable system. Cellular skylight shades are the most common answer because they insulate the biggest heat-loss surface in the room. Motorisation is close to mandatory on anything out of reach.

Angled tops, portholes, octagons and triangles are all built to a template rather than to a width and drop. Cardboard or laser templates, plus a photo of the opening with the frame depth visible, prevent the most expensive remakes in the trade.

Traffic is the constraint, not light. Verticals and panel tracks stack clear of the operating panel; a wide roller shade over a patio door will be in the way every time somebody steps outside.

• Frame depth at the shallowest point, for inside mounts.
• Handles, cranks and tilt-and-turn hardware that a blind would foul.
• Where the arch spring line meets the rectangular window below it.
• Existing trim you'll need to match or extend.
• Bay corner posts and the angle at each junction.