Window Mechanism Measuring Guide (Espagnolette / Shootbolt)
Handles & Hinges UPVC Maintenance Ltd is a UK specialist in replacement parts for UPVC windows and doors. Use this guide to record the key sizes of your window locking mechanism (espagnolette or shootbolt) so you can order the correct replacement quickly.
What to measure (in order)
-
Type of mechanism
Look along the sash edge: a straight espagnolette strip with mushroom/roller cams, or a shootbolt system with extending bolts at the ends (some are telescopic/quick-fit). -
Overall strip length
Measure end-to-end metal length of the locking strip (not including loose keeps). Telescopic types may self-set; note the min/max if marked. -
Backset (handle position)
Distance from the outer faceplate edge to the centre of the square spindle hole in the gearbox. On many UPVC windows this is around 20–22 mm — measure yours. -
Faceplate width
Measure the width of the metal faceplate that screws to the sash (often ~16 mm on UPVC systems). -
Cam / mushroom layout
Count cams/rollers and note their spacing from the gearbox centre (e.g., “first cam 180 mm up, second 420 mm down”). If shootbolts are fitted, note the throw length. -
Handing & sash type
Side-hung vs top-hung. Some strips are universal/reversible; still record handing in case your make/model requires it. -
Brand or code
Check the gearbox/faceplate for a stamped brand (e.g., ERA, GU, Roto, Yale, Winkhaus, Mila) or part code. A photo helps.
Quick reference table
| Measurement | How to take it | Why it matters |
|---|---|---|
| Type | Visual: espag with cams / shootbolt ends | Identifies family of parts |
| Strip length | End-to-end metal | Ensures correct reach and cam positions |
| Backset | Faceplate edge → spindle centre | Aligns handle and gearbox |
| Faceplate width | Measure metal rail width | Fits sash Eurogroove / channel |
| Cams / rollers | Count and record distances to centre | Compatibility with existing keeps |
| Handing / sash | Side-hung or top-hung | Some strips/keeps differ by hand |
| Brand / code | Stamped on faceplate/gearbox | Speeds up exact matching |
Measuring tips
- Photograph the gearbox, the whole strip, and the nearest cam/keep area for reference.
- If your strip is telescopic, set the sash to the closed line and note the length where both ends engage evenly.
- When replacing just the strip, re-use compatible keeps or replace them as a set to match new cam geometry.
FAQ
Backset vs faceplate width — what’s the difference? Backset is the handle spindle position relative to the faceplate edge; faceplate width is the actual metal rail width that sits in the sash channel.
Can I swap an espag for a shootbolt? Sometimes, if the system supports it and keeps/clearances are correct. Many prefer a like-for-like replacement for quickest fit.
Why don’t my cams line up with the old keeps? Cam spacing varies by make/length. Either adjust/replace keeps or match a mechanism with the same layout.