XO or OX? How to tell which sliding door you have

What the letters mean

A sliding patio door is described by its panels, one letter for each:

• X is a panel that slides. Manufacturers call it the operating panel.
• O is a panel that does not move. It is called the fixed or stationary panel.

The letters run from left to right as you stand outside, facing the door. Andersen states the rule plainly for its 100 Series: "X=Operating and O=Stationary," and "if the operating patio door panel is on the left from the exterior, the unit will be XO handed."

So a two-panel door with one fixed panel is one of two things:

• XO: from outside, the sliding panel is on the left.
• OX: from outside, the sliding panel is on the right.

Andersen's diagrams label them the same way. An XO unit has an "operating left panel / stationary right panel." An OX unit has an "operating right panel / stationary left panel."

Why you read it from outside

The same door is XO from one side and looks like OX from the other. Without an agreed side, the letters mean nothing. Andersen says it hands all of its windows and patio doors from the exterior of the home, with occasional exceptions that its product articles cover. For gliding doors:

"Gliding patio door units are handed from the exterior of the home, based on the location of the operating panel when viewed from outside."

The same article adds that if the operating panel is on the left, the unit is left-handed, and that "the unit is handed as a whole."

This page uses Andersen's wording because Andersen is the maker whose documents we opened that spell the rule out. Other manufacturers use the same letters. Marvin, for example, lists OX and XO for its two-panel sliding doors. Marvin's manual does not say which side the letters are read from, so if your door is not an Andersen, check its maker's own documents before you rely on the code to order a part.

How to work it out

1. Go outside and stand facing the door.
2. Find the panel that slides. Open the door a little if you are not sure; that is the real test. A closed screen can be a hint, since JELD-WEN's vinyl patio door guide says the insect screen is mounted on the exterior side of the operating panel, but a screen that has been slid open sits in front of the other panel.
3. Write the letters left to right. Sliding panel on the left: XO. On the right: OX.

If you cannot get outside, for example because the door will not open or the outside is not safely reachable, work it out from inside and reverse it. Andersen recommends viewing the unit from the exterior, and says that when that is impractical, "the handing reference will need to be reversed." From inside, a sliding panel on your right is on the left as seen from outside. That door is XO.

Do not take the door apart to check. Everything here is done by looking.

Doors with three or four panels

Larger doors use more letters, in the same order. Marvin's manual for one of its sliding doors lists these configurations:

• two panels: OX, XO;
• three panels: OOX, XOO, and OXO;
• four panels: OXXO.

An OXXO door has two sliding panels in the middle, with a fixed panel at each end. Andersen notes that its four-panel gliding doors "have a right and left-hand operating panel." Marvin also adds LH or RH to its OXO and OXXO codes. Its manual does not explain those suffixes, so this page does not either.

When the configuration matters

Ordering a handed part. Some parts are made for one handing. On Andersen's 100 Series, insect screens "are handed the same as the unit," while "rollers, locks and weatherstrip are not handed." That list is Andersen's, for one product line, and the Andersen 100 Series guide covers that line's other parts. Other doors differ. On Andersen's 400 Series Frenchwood gliding door, for example, the handles, the frame or jamb weatherstrip, and the exterior keyed locks are handed the same as the unit, while the screens and rollers are not; the Frenchwood gliding door guide lists the rest. Andersen's two 200 Series gliding doors, the Perma-Shield and the Narroline, hand some parts differently from each other, and the Andersen 200 Series gliding door guide lists which. Ask the maker or a technician which parts on your door are handed. For a Milgard door, the Milgard sliding patio door guide shows where to find the Sales Order number Milgard uses to identify each door, which Milgard asks for on a service request.

Describing the door. In a repair inquiry, "XO, sliding panel on the left from outside" is clearer than "the door that opens to the left." It also means nobody has to guess which side you were standing on.

Telling a fixed panel from a stuck one. Not every door has a fixed panel: JELD-WEN says one panel may be fixed and at least one operates. If your door does have a fixed panel and you are not sure whether the panel that will not budge is a stuck slider or the fixed one, the configuration tells you which one is supposed to slide.

Write it down

Add the configuration to the printable door record card, which keeps the code, the maker, and the door's repair history in one place. If you do not know the maker, the maker label guide shows where to look. If you are asking about a repair, the photo guide lists what else to capture.

Where to go next

• A panel that drags, sticks, or rolls roughly is usually covered on the roller repair page or the track repair page.
• A handle or lock that does not work is covered on the locks and handles page. Lock handing is one reason the configuration matters: before ordering a lock that sits in the panel's edge, the mortise lock replacement guide covers what to identify first.

To ask about a repair in Plano, Allen, McKinney, or Frisco, describe the door, including its configuration if you know it, on the contact page. The operator reviews every inquiry and replies with the next step. Sending the form is not a booking.