Bi-fold Doors Trade Prices
part of Saleglaze Ltd Group EST 1984
URL Price your doors in less than a minute! Get a Quote NOW >

Bi-fold Glossary of Terms

Cill Horns

A projection cill which is wider than the opening is said to have cill horns. The amount of extra door cill each end can be varied.

Low Threshold

The threshold is the bottom of the door which you step over as you go in and out of the door. A low threshold is not as high as a standard threshold - making access easier. Weather performance is reduced when compared to a standard threshold - but is ideal for internal applications between rooms or possibly external applications in sheltered areas.

Standard Threshold

The threshold is the bottom of the door which you step over as you go in and out of the door. A standard threshold offers the best weather performance - but is higher overall than the low threshold (Severe Weather Rating).

Face Drainage

A slot in the outer-frame to allow excessive water to drain out from the outer-frame. The slot is covered by caps to hide the hole.

Traffic Door

A door that can be used like a standard hinged door without having to fold the other panels to use it. With a traffic door you can enter the room from outside. Without a traffic door you cannot enter the room from outside.

Trickle Vents

A ventilation system to allow fresh air into the room whilst keeping the doors closed/locked to maintain higher air quality. Traditional 'trickle vents' are fitted in the head extension of the outer-frame to achieve the ventilation required.

RAL / KL / BS Colours

A paint industry standard way of referring to different colours. You choose a RAL / KL / BS colour reference from a colour chart. You can specify a gloss level of your paint too. The gloss level options are Gloss, Semi-Gloss and Matt.


Part of the locking system which is fitted to the mullions. Shoot-bolts are bars which slide up from the door sash into the frame - securing both the top and bottom of the door.


Also known as "polyamide thermal break". Part of the Aluminium extrusion which thermally separates the front and the back of the Aluminium - thus keeping the cold outside Aluminium physically away from the Aluminium on the inside of the door.