The bikes must always be returned to a station.
In case of a short break, it is possible to use the lock in allocation to all the bikes.
First of all, be sure to check that the lock's key is present. You can find it under the basket: if the key is missing, the bike cannot be tied.
you find the black wire in the basket; this is the one to be used for securing a bike to a stake or railing
put the top of the wire within the hole under the basket, take out the key and keep it with yourself