yama

Errm....

If I lock two u-locks together, how many locks do I have to open to separate the locks again?

I'n not locking my lock to the bike, but to the other guys u-lock... this difference makes a difference...

And for the u-lock that is lying on the floor after the other person left: I am using two ulocks, the first one secures frontwheel AND frame, the second one secures the backwheel to to the frame. Only this one I meant to interlock with another u-lock, so in the lock are 1. frame, 2. rearwheel and 3. the others persons lock (not bike!).

So if anybody manages to cut the bikerack at one point (depends on the structure of the rack of course) and get out the u-lock of my neighbour, it is still clinging to my u-lock, which clings on my bike, which clings on another part of the bikerack, which is hopefully not compromised by the first cut. See now what I mean? I saved your bike from being stolen in that case by locking my lock into ur lock.