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Thumbturn euro cylinder or key both sides

Updated: October 2026

You are choosing the inside of a euro door, and a thumbturn looks easier than hunting for a key when you leave. It is also a handle for anyone who can reach it through glass, a side light or a letterbox. Use a thumbturn when the inside must open without a key and a hand outside cannot reach the turn. Use key both sides when that reach exists. The [lock cylinder comparison](/hub/door-and-window-security/lock-cylinder) lists which of these ten are turns and which are doubles. Peter F. used those listings and public UK guidance in October 2026. A qualifying purchase can earn a commission at no extra cost to you.

You are choosing the inside of a euro door, and a thumbturn looks easier than hunting for a key when you leave. It is also a handle for anyone who can reach it through glass, a side light or a letterbox.

Our top picks

greenteQ greenteQ Orion 35/35 thumbturn

Best overall

greenteQ greenteQ Orion 35/35 thumbturn
8.6/10about £32.06
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XFORT XFORT 50/50T thumbturn

Rank 2

XFORT XFORT 50/50T thumbturn
7.6/10about £13.99
View offer
XFORT XFORT 50/50 euro cylinder

Best value

XFORT XFORT 50/50 euro cylinder
7.8/10about £13.99
View offer
On this page
  1. 1.What the turn actually changes
  2. 2.When the turn is the weak side
  3. 3.Escape doors and HMO bedrooms
  4. 4.Which listings are turns, and which are keys

What the turn actually changes

A thumbturn euro cylinder is key outside and a turn inside. You lock the street side with a key and leave by turning the knob. 35/35T and 50/50T put the turn on the inside when they are fitted as the listing describes. The T is the handing, not a brand, and these thumbturns are not something to reverse the way a symmetric double sometimes can be. The daily complaint in the XFORT 50/50T reviews, 4.6 from 5,574 at about £13.99, is a key left inside a double cylinder, which locks you out. The Valorada 35/35T, 4.5 from 75 at about £10.49, is used for the same reason. On the top pick, the greenteQ Orion, one buyer found the outside key would not lock unless the thumbturn sat in a particular position. Test that with the door open.

When the turn is the weak side

The turn that lets you out also lets someone else in, if they can put a hand on it. Letterboxes, side lights and vision panels are the usual routes. In that house, key both sides is the security choice. The best value in the comparison, the XFORT 50/50 at about £13.99, is that key-both-sides shape, not a turn. NPSA allows a thumbturn where the turn cannot be reached if the glass breaks. None of these listings prints BS 8621 or BS 3621. If a hand can reach the inside from the street, do not fit a turn. The how to change a euro cylinder page is where the T side is fitted inside, within 3 mm of the furniture.
greenteQ greenteQ Orion 35/35 thumbturn

Testsieger

greenteQ greenteQ Orion 35/35 thumbturn
8.6/10about £32.06
View offer

Escape doors and HMO bedrooms

The DASH guide for HMO locks, 2023, says a key on the inside of an HMO bedroom is not acceptable, and the thumbturn must not be reachable through glass. That is a rule for those rooms, not a rule that every house front door must have a thumbturn. Approved Document Q applies to new dwellings, and it does not require a thumbturn on every new front door. A letterbox door can need a key while a bedroom exit needs a turn. Read the policy if the door is named in it.

Which listings are turns, and which are keys

Four thumbturns sit in this set. Valorada 35/35T at about £10.49 and XFORT 50/50T at about £13.99 have no TS007 line. greenteQ’s Orion at about £32.06 states a TS007 3-star Kitemark. Federal’s Gabriel at about £37.99 states TS007:2024 and Sold Secure Diamond. The best lock cylinder page weighs those claims. The higher-mark cylinders here are turns, so a key-inside requirement is a different product. The doubles are Wavanta 30/35, Valorada 35/35, DIDA 40/40 and the XFORT 50/50. None states TS007 or Diamond. A 50/50T will not suit a 35/35 door. The outside mark is the anti-snap euro cylinder page. It does not cancel a letterbox.

Common questions

Can someone open a thumbturn through the letterbox?
Yes, if they can reach the turn. That is the reason to keep key both sides on a door with a letterbox, a side light or a vision panel within arm’s length of the knob. NPSA’s guidance allows a thumbturn where the turn cannot be reached, including if the glass breaks. If you can already picture a hand on the knob, choose the double.
Do new-build rules force a thumbturn on my front door?
No. Approved Document Q covers security in new dwellings and does not require a thumbturn on every front door. Escape guidance that asks for keyless exit applies to the doors it names, such as certain fire exits and, in the DASH guide, HMO bedrooms. A householder’s own front door is not under that bedroom rule.
What about an HMO bedroom?
The DASH guide says a key on the inside of an HMO bedroom is not acceptable, and the turn must not be reachable through glass. That is landlord guidance for those rooms in houses in multiple occupation. It is not an instruction to put a thumbturn on every door in an ordinary house. If the bedroom door has glass next to the turn, the guide’s second sentence still applies.
Which thumbturns here state a security mark?
greenteQ states a TS007 3-star Kitemark. Federal states TS007:2024 and Sold Secure Diamond. Valorada 35/35T and XFORT 50/50T do not. The marks are listing lines without a certificate number in the file. A cheap turn can still be the right inside for a low-risk door. It is not the stated 3-star upgrade.
The outside key sometimes does not lock. Why?
On a thumbturn, the inside knob can be left in a position that holds the cam. One greenteQ reviewer had to set the turn before the outside key would lock. Try that with the door open. If it only locks in one awkward position, that unit is not doing the job the reviews generally describe, and it is a reason to return it rather than to live with a door you cannot secure from the street.

Related pages

Lock cylinder buying guide

Lock cylinder

Best lock cylinder: street door, swap or night latch

How to change a euro cylinder without leaving it proud

Anti-snap euro cylinder: what TS007 actually means

Sources

Public UK sources for the security rules, plus the amazon.co.uk listings in this set. Last checked 21 October 2026.

  1. West Yorkshire Police, euro-cylinder advice (retrieved 21 October 2026)
  2. West Yorkshire Police, door and window advice (retrieved 21 October 2026)
  3. Door & Hardware Federation, TS 007 (retrieved 21 October 2026)
  4. Master Locksmiths Association, domestic security guidelines, January 2025 (retrieved 21 October 2026)
  5. GOV.UK, Approved Document Q (retrieved 21 October 2026)
  6. Sold Secure, domestic security booklet (retrieved 21 October 2026)
  7. Lock and Key, how to measure a euro cylinder (retrieved 21 October 2026)
  8. DASH, locks on doors in HMOs, 2023 (retrieved 21 October 2026)