On the morning of Monday, 6 July 1942, the Frank family moved into their hiding place, a three-story space entered from a landing above the Opekta offices on the Prinsengracht, where some of Otto Frank's most trusted employees would be their helpers. This hiding place became known as the "Achterhuis" (translated into "Secret Annex" in English editions of the diary). Their apartment was left in a state of disarray to create the impression that they had left suddenly, and Otto left a note that hinted they were going to Switzerland. The need for secrecy forced them to leave behind Anne's cat, Moortje. As Jews were not allowed to use public transport, they walked several kilometres from their home. The door to the "Achterhuis" was later covered by a bookcase to ensure it remained undiscovered.