One letter on a purchase order decides whether a container of doors gets installed or stacked in a warehouse waiting for a claim. Learning how to determine door handing takes ten minutes; arguing about it after the doors land takes six weeks and usually ends with you paying freight both ways.
Door handing is the convention that names which side the hinges sit on and which way the leaf swings, stated from a defined reference side. The trap is in those last four words. North America and Europe use different reference sides, and North America uses two of its own. "LH" is not one door — it is at least three, depending on who wrote it.
The Three Conventions Sitting on the Same Order
| Convention | Where you stand | Hand is named by | Typical marks |
|---|---|---|---|
| ANSI/BHMA commercial (US) | Outside / secure side (the key side) | Hinge side, plus "reverse" if the leaf swings toward you | LH, RH, LHR, RHR |
| US residential trade | The side the door swings toward you | Hinge side, plus inswing/outswing stated separately | LH inswing, RH outswing |
| DIN / EN (Europe) | The side the door opens toward (pull side) | Hinge side | DIN links (L), DIN rechts (R) |
Two published equivalences are worth memorising, because they are where most transatlantic mix-ups happen: right-hand outswing (RHOS) equals left-hand reverse (LHR), and left-hand outswing (LHOS) equals right-hand reverse (RHR). A US residential buyer and a US commercial specifier can describe the same physical door with opposite letters and both be correct in their own system. Handing terminology for windows and pedestrian doors in Europe sits under DIN EN 12519, while the international spread of methods is catalogued in this survey of door handing conventions by the door-hardware standards community.
Here is the sentence to keep: a handing letter without a stated reference side is not a specification, it is a guess.
Your Next Move Depends on Who Sent the Order
Scenario A: A US buyer writes "RH inswing", nothing else
Most likely they are using the residential convention: standing where the door swings toward them, hinges on the right. If they are a commercial door distributor, they may mean the ANSI convention instead — same words, mirrored door.
Do this: reply with a plan-view sketch showing the hinge side, an arc for the swing, and the words "viewed from exterior". Ask them to confirm the sketch, not the letters. If they confirm a picture, a later dispute has a picture in it.
Scenario B: A German or Austrian buyer writes "DIN R"
DIN rechts means hinges on the right when you stand on the side the door opens toward you. This maps cleanly to a physical door, but it does not map cleanly to the letter your US-trained production planner will write on the work order.
Do this: convert once, at order entry, and record both notations in the order file: "DIN R = hinges right, opens toward viewer". Never let DIN letters travel down to the shop floor untranslated. Hinge mortise position is cut before anyone re-reads the PO.
Scenario C: The buyer sends only a photo of the old door
This is the most common case in renovation-driven markets, and the photo almost never says which side it was taken from.
Do this: ask one question — "were you standing inside or outside the room when you took it?" — and ask for a second photo showing the hinges. Two photos and one sentence resolve what three emails about letters will not.
Scenario D: Commercial project, fire-rated or egress door
Here handing carries a code consequence, not just a fit consequence. Egress doors in many jurisdictions must swing in the direction of travel, and fire-rated assemblies must be listed for the configuration supplied. Getting the hand wrong is not a fit problem; it is a rejection at inspection.
Do this: require the door schedule, not a letter. A door schedule states hand, swing, fire rating, frame type and hardware prep per opening. If the buyer has no schedule, treat the order as engineering-incomplete and say so in writing before you cut steel.
Scenario E: The buyer says "just send both"
Sometimes offered for small quantities. It sounds generous and it is usually a trap — you carry two SKUs, two hardware preps and a return you cannot resell.
Do this: offer a reversible or field-handed product if your line has one, and price it as such. Otherwise decline politely and go back to the sketch.
Decision Matrix
| What the order says | What you must confirm | How to confirm it |
|---|---|---|
| LH / RH only | Which convention, which reference side | Plan-view sketch + "viewed from exterior" |
| LHR / RHR | Confirms ANSI commercial; verify outswing is intended | Sketch + confirm egress direction |
| DIN L / DIN R | Reference side is the opening side | Convert at order entry, record both notations |
| "Inswing" / "outswing" only | Hinge side still unknown | Ask for hinge side or a photo of the hinges |
| Photo only | Where the photographer stood | One question + a hinge photo |
| Nothing stated | Everything | Do not schedule production |
What Actually Removes the Ambiguity
Letters travel badly. Drawings do not.
The fix that ends handing disputes is a small plan-view diagram attached to every quotation and every order confirmation: the wall line, the leaf shown at 30 degrees, an arc for the swing, the hinge side marked, and a label that names the reference side in words — "viewed from exterior" or "viewed from corridor". Add the leaf dimensions and the opening dimensions to the same image and you have removed the two most expensive misunderstandings in the door trade at once, because the other one is the rough opening. If that part of the order is still fuzzy for you, rough opening vs unit size covers the three numbers that belong on every door order, and standard door sizes gives the nominal sizes buyers assume when they do not say.
Two habits make the diagram trustworthy rather than decorative:
- Dimensions must be measured, not drawn to look right. A swing arc is a symbol; a leaf width is a fact. Mixing the two on one image is how a 900 mm leaf gets ordered against an 890 mm opening.
- The reference side goes in text, not in a symbol. Arrows get flipped when images are mirrored for a catalogue layout. The words do not.
Next Steps
Pick whichever of these you do not already do:
- Add a handing field to your order form with three sub-fields: convention used, reference side, hinge side. Free text invites letters; three fields invite answers.
- Put a plan-view handing diagram in the quotation template. One drawing per opening, reused across the order.
- Standardise how the diagram gets made. Tracing arrows by hand in a photo editor works until volume rises; a dimension-annotation tool that snaps to the real edges of the drawing and locks the measured leaf and opening sizes onto the image keeps the numbers honest as the catalogue grows. This is also where AI image tools fail badly — a generated door image can look convincing and carry a swing arc that was never derived from your product, and a plausible-looking wrong number is worse than no number.
- Build a one-page handing conversion sheet for your sales team covering ANSI, US residential and DIN, and staple it to the order desk. For the wider set of drawings that go out with building-product orders, building material spec diagrams shows what a complete sheet looks like.
Order-Entry Checklist
- Handing convention named explicitly on the order (ANSI / US residential / DIN)
- Reference side stated in words, not implied by an arrow
- Hinge side confirmed separately from swing direction
- Inswing/outswing confirmed against the buyer's egress or code requirement
- Plan-view sketch attached and confirmed by the buyer in writing
- Leaf size and rough opening size both stated, both measured
- For fire-rated or commercial work: a door schedule exists, per opening
- Order file records both the buyer's notation and your internal notation
FAQ
How do I determine door handing quickly?
Stand on the outside of the door — the side you would lock it from — and look at which side the hinges are on. Hinges left is left hand, hinges right is right hand under the ANSI commercial convention. Then state which side you were standing on, because that sentence is what makes the letter mean anything.
What does LHR mean on a door order?
LHR is left hand reverse: hinges on the left when viewed from the secure side, with the leaf swinging toward you rather than away. It is the ANSI commercial notation for what a residential seller would usually call a right-hand outswing door.
Is DIN left the same as left hand?
Not reliably. DIN handing is read from the side the door opens toward, while ANSI handing is read from the secure side, so the same door can be DIN links and right hand. Convert once at order entry and record both notations rather than trusting that the letters match.
What is the difference between inswing and outswing?
Inswing means the leaf swings into the room or building; outswing means it swings out. Inswing and outswing describe direction only — they do not tell you the hinge side, so an order that says "outswing" without a hand is still incomplete.
Can I just send a reversible door instead?
Only if the product is genuinely field-handed, including the hardware prep and any weatherstrip or threshold. Shipping a non-reversible door and hoping the installer copes converts a handing question into a warranty claim.