This may seem to be pretty self explanatory – after all, you put your ticket in the machine and walk through the turnstile, right? Well, yes, but many tourists to Barcelona do it the wrong way round: they put their ticket in the right hand slot and then try to go through the turnstile on the left, which is not possible. Instead, you need to put your metro ticket in the left slot and pass through the turnstile on the right. Get it wrong when it is really busy and you could lose your ticket!
Just to confuse things a little more, if the ticket validation machine has glass sliding doors rather than a turnstile, then you do put your ticket in on the right and enter on the left! These entrances can currently be found at Catalunya and Barcelona Sans station for the RENFE entrance. If you’re not sure what to do when the time comes just hang back for a couple of seconds and watch the locals – you’ll soon get it.