Identify Door Lock type (How to)

[Diyisfun]

I have a Yale lock (cylinder) fitted to folding bi-fold patio doors, I cant lock from the outside, I am guessing I need a new cylinder. How do I know what I need? do I have to take it out to identify?
I have tried other keys & WD40.

 

[footprints]

Best to post some photos someone will know the type

 

[Diyisfun]

Just taken the cylinder off, no markings on it, I think its all about the length.
Trip to Toolstation with the cylinder for me.

 

[JohnD]

you decided against posting photos, then?

 

[footprints]

If it is a eurolock type you measure each end to the centre some are equal some longer on one side than the other.

 

[kingandy2nd]

http://www.upgrademylock.com/upgrade-my-lock/how/

 

[Diyisfun]

you decided against posting photos, then?

There was no point in photo, I have taken them, its a Yale lock.
You measure each side.

 

[Diyisfun]

http://www.upgrademylock.com/upgrade-my-lock/how/

Thanks for that, I found similar on the Yale web site.