Ah, the "which side does what" question.
I was at a large construction site in London's Famous London last week. I've done the induction course, been fingerprinted*, shown my passport, so got issued with a magnetic card to work the turn stile.
Go in fine. Meet sub contractor, do things, time to go. Get to row of turnstiles, get card out, slap it on the reader, push turnstile. Beep. No movement. Try again. Same result. Arse. Finally realise that the layout is for right handed people, while I'm left handed, so I'd been tapping my card on the reader for the adjacent turnstile.
*more accurately had my index finger read by their biometric wotsit.