Formal — to staff
Sento · Bathhouse
You
サウナに入りたいのですが、この鍵はどうやって使えばいいですか？
さうなにはいりたいのですが、このかぎはどうやってつかえばいいですか？
I'd like to use the sauna, but how do I use this key?
Romaji: Sauna ni hairitai no desu ga, kono kagi wa dō yatte tsukaeba ii desu ka? / Reply Romaji: Sauna no doa no totte ni, sono fukku o hikkakete temae ni hiku to akimasu yo.
Reply
サウナのドアの取っ手に、そのフックを引っ掛けて手前に引くと開きますよ。
さうなのどあのとってに、そのふっくをひっかけててまえにひくとあきますよ。
Just hook that plastic key into the slot on the sauna door handle and pull it toward you to open it.
Gesture & etiquette
Hold up the plastic/metal hook-style sauna key to show the receptionist or another guest.
Never enter the sauna without paying the extra fee. The special hook key is proof of payment; wearing it around your wrist/neck is mandatory in many sentos.