How do I identify window and door hardware to order the right spare?

Window and door hardware is made by a fairly small number of manufacturers and sold under dozens of names, and the part you need is nearly always still available if it can be named. The reason people end up replacing whole windows for the sake of a stay is that they never found the marking, not that the part was obsolete.

Step by step

1. Look on the part before you measure it.Multipoint lock faceplates and espagnolette lock strips are marked near the gearbox. Friction stays carry a name and a size on the underside of the arm or on the track. Handles are marked on the back of the backplate, visible once the handle is off. Hinges are marked on the leaf edge.
2. Clean the marking and photograph it straight on.Decades of paint, dirt and lubricant hide these. A wipe with a solvent-free cleaner and a raking torch beam make a mark readable that looked blank. Photograph square-on, in focus, with the phone's flash off and a torch to one side.
3. Search the exact string, not a description.Hardware reference numbers are distinctive. Typing the stamped string into a search will very often land directly on a supplier's product page, complete with the dimensions you would otherwise have measured.
4. Find the frame's own label if the part is unmarked.Most uPVC windows and doors carry a small label or an etched mark on the frame, often in the hinge rebate, on the outer frame under the sash, or on the glass unit spacer bar. It names the system or the fabricator and frequently carries a date.
5. Look at the sealed unit spacer.The metal or composite spacer bar inside a double glazed unit usually carries the manufacturer and the date of manufacture, readable through the glass at the right angle. It will not name the hinge, but it dates the window, which narrows the hardware generation considerably.
6. Dig out the installation paperwork.The original quotation, the guarantee, and any FENSA or equivalent certificate name the installer and often the window system. The installer, if still trading, can look the hardware up from the job number in a couple of minutes.
7. Measure only what is left over.Once the part is named, its dimensions are in the catalogue. Measure to confirm rather than to identify — it is far quicker and far less error-prone in that order.
8. Take the old part to a specialist if you are stuck.Dedicated window and door hardware suppliers, including trade counters and online specialists, identify parts from photographs every day. A clear photograph with a rule alongside for scale gets an answer from most of them.
9. Record what you find.Once you have identified a friction stay or a lock, write the reference and the size down. The other windows in the house are almost certainly the same system, and you will need it again.

Tips

• Photograph the part in place before removing it as well as after. Orientation and handing are frequently the thing that is wrong on a replacement.
• If a part is genuinely obsolete, ask specifically about a 'universal' or 'adaptable' equivalent. Manufacturers make these precisely for the discontinued-part market.
• Buy two of a cheap part like a friction stay while it is identified and in stock. The second window will fail within a couple of years and the price of the spare is trivial.

Common mistakes

• Describing the part instead of naming it — 'A silver window hinge about 12 inches long' matches hundreds of products. A stamped reference matches one.
• Assuming a discontinued system means no parts — Hardware manufacturers outlive window fabricators, and the hinge in a defunct fabricator's window was bought in from a company still making it.
• Stripping the window before sourcing the part — An opening window with the stay removed cannot be secured or closed properly, and identification is easier with the part in context anyway.