Terms you may come across when looking at double glazing


Opening portion of a window or door (not including the glass or panel in it).


A shaped piece of glass that is glued (with clear U V curing glue) to the main piece of glass.

Internal or integral Blind

A Venetian or pleated fabric blind that is within the cavity of a sealed unit.

Vertical Slider

A Pvc-U/ aluminium replacement for a box sash window where the sashes slide up and down in the frame, the weight is balanced out by a spring on each side of the window. Most of these windows can also tilt in for easy cleaning if at height.

Tilt and Turn

A window that opens in two ways. Turn the handle 90 degrees and the top of the window tilts in to allow a good amount of ventilation, and if you turn the handle (from the close position) 180 degrees the window will open from the side inwards 90 degrees. Normally used in flats to allow safe ventilation during normal use, but can also be opened up fully to clean from the inside. Old versions of this type of window work in reverse (turn and tilt).


A term used to describe a standard window where the sashes open outwards. Includes both top and side hinged sashes.


A horizontal bar across the window or door.

Composite door

A door that looks like a traditional wood door, but is made up of GRP (glass reinforce plastic) outer skins and a wooden frame inside with foam insulation.


A profile at the bottom of window or door that protrudes out from the wall on the outside to direct water away from the property.


An extension of the window/door cill into the brickwork.

Diamond cut

Now called Brilliant cut. A decorative V groove in the glass, normally in a diamond or square pattern. An alternative to a decorative lead design.


A decorative stick on lead in a design to mimic traditional lead that was used to join pieces of glass together.

Colour leads

A decorative stick on lead and coloured film that is used on a piece of glass to mimic traditional stained glass windows.

Soldered joint leads

The joints of the decrative lead is soldered for a more realistic look.

Box Sash

A Georgian/Victorian window where the sashes slide up and down. The weight of the sash is balanced out by a cast iron weight and pulley system each side that is boxed in with architraves.

Door cassette

Two trims that clip or screw together around the glass of a composite door to hold the glass in.


Pvc-U (in raw state normally comes is small pellets) that is then heated and extruded through a die into a shaped length (usually cut to 6 meters long) for quick assembly of windows and doors.


correctly is PVC-U which is Polyvinyl Chloride – Unplasticised. A long life recyclable type of rigid plastic.

Sealed unit

(Hermetically sealed units). Two pieces of (usually 4mm) glass that are sealed together with an air gap between them (nowadays either 16 or 20mm) by ways of an aluminium spacer bar around the edge and sealed with hot melt (a Butyl based sealant).

Warm edge spacer

A alternative spacer bar for sealed units that allows less heat transference which lowers the u value of the sealed unit.

Toughened glass

A safety glass that goes through a heat process that changes the structure of the glass so that it is stronger and if it does break, breaks into small pieces.

Laminated glass

Two pieces of glass with a film sandwiched between them. Standard is 6.4mm (3mm glass, 0.4mm laminate, 3mm glass). A more complex build up can also be used with multiple layers to create bullet proof glass.


A trim that clips into the window frame or sash that holds the glass in place.

Shoot bolt

Locking rods that come out of the adjacent sides of a window or door for additional locking points.

Multipoint lock

A lock that has more than one locking point.

Multipoint door lock

A door lock that is concealed in the side of the door sash with multiple locking points. A Multipoint lock does not include the handle or barrel.

Euro Barrel

The key operated mechanism of a door lock.


A vertical bar dividing a window or door.

Espagnolette lock

A type of window lock (usually multiple points 2-8) where the lock is concealed in the side of the sash so when the window is closed all that is visible is the window handle.


The process or extruding PVC-U profile with a gasket attached.


The profile used for the main outer frame of the window.

Deep outerframe

The profile used mainly for the main outer frame of a door or tilt and turn window.

Internally beaded

Where the glass and beads are put into the frame/sash from the inside of the property.

Externally beaded

where the glass and beads are put into the frame/sash from the outside, this way has to have a special way of glazing or the property would not be secure.


Pvc-U profile is joined together by heating to around 250 degrees C and pressed together in a specially designed machine.

Reverse butt welding

A term used where all the joints are welded together. Normally associated with internally beaded windows.

Mechanically joined transoms

A term used where although the frame may have welded joints, the transoms and mullions are milled and screwed in place.


Convex profile (The shape of the profile has a curved part that protrudes outwards).


Concaved profile (The shape of the profile has a curved part that protrudes inwards).

Georgian bar

A decorative bar inside the sealed unit to mimic the multiple small panes of glass used in the Georgian period to make up a window. This was due to the limited size that glass was able to be produced at, at the time.

Stick on bar

A decorative bar that is stuck on the outside of a sealed unit to mimic Georgian period windows.


A galvanised steel, aluminium or PVC-U product that is put into the chambers of the profile to increase the strength of the profile.

Low e glass

Low e stands for low emissivity glass. This glass has a special metallic coating that lets the energy from the sun in while reducing the heat lost outwards.


A rubber strip that is either between the PVC-U and the glass or two PVC-u profiles, to create a weather proof seal.

Head drip

A trim on the top of the window or door that directs water from above away from the face of the window or door.

Friction stay

The type of hinges used on a casement window that allows a slight resistance eliminating the need to have a casement stay to hold the window open.

Egress hinge

A friction hinge that opens 90 degress and then when a button is pressed on each hinges, it allows the sash to slide along, allowing access for cleaning of the outer pane of glass from inside. Also know as fire escape hinge.

Contact Info

Thermoshield Windows
11-13 Purdeys Way
Rochford, Essex SS4 1ND
01702 541841