What are the four main cylinder lock form factors you'll see on European doors?
Cylinders come in four practical shapes — round-double, round-half, round-with-knob, and profile-double — all with the same internal pin-tumbler mechanism but different mounting.
* The four common cylinder form factors — round double, round half, round with thumbturn, and Euro profile double. *
The four types:
| Type (DE) | English | Where used |
|---|---|---|
| Rundzylinder-Doppelzylinder | Round double-cylinder | Older European interior doors; key on both sides |
| Rundzylinder-Halbzylinder | Round half-cylinder | Cabinets, mailboxes, garages — only one keyhole |
| Rundzylinder mit Drehknopf | Round with thumbturn | Apartments — key outside, knob inside (so you don't need a key to leave) |
| Profilzylinder-Doppelzylinder | Euro profile double-cylinder | The standard for modern European front doors |
Why "Profil" beat "Rund":
The Euro profile (DIN 18252 standard cross-section) lets any manufacturer's cylinder fit any manufacturer's door. Before standardization, every lock brand had its own dimensions and you were locked into one supplier. Today, you can swap a cheap profile cylinder for a high-security one (with anti-drill, anti-pick) without changing the door hardware.
Sizing — important when buying replacements:
Profile cylinders are sized "30/30", "30/40", etc. — the two numbers are the lengths in mm of the two halves measured from the central screw hole. A cylinder that protrudes more than 3 mm beyond the escutcheon can be snapped off with pliers — a common burglary technique. Always measure correctly.
Tip: When you see the anti-snap marketing label, it means the cylinder has a deliberate weak point that breaks off harmlessly without exposing the locking mechanism. Worth the extra ~15 CHF on a front-door cylinder.