The guide is not an accessory

Guides are quoted as a line item and treated as trim. They set the friction, the noise and the wind resistance of the whole door.

The guide is the channel the curtain runs in at each side of the opening. It appears on a quotation as a line item alongside brackets and fixings, which understates what it does.

Three things depend on it. Friction, because every cycle of the door drags the slat ends along that channel, and friction is load on the operator. Noise, because a slat running dry in a metal channel is the loudest thing about a shutter — which is why the guides carry felt and rubber seals. And wind resistance, because the guide is what holds a closed curtain in the opening when the pressure comes.

Guides are profiled for the curtain they carry: a single-skin curtain and a vented one present different slat ends and need different channel depths. A guide matched to the curtain also coats with it, so the door leaves the plant one colour.