People wore long flowing robes. They would tuck them into their belt to keep the robes out of the way while they worked. AT: "Tuck your clothing into your belt so you are ready to serve" or "Be dressed and ready to serve" (See: [[rc://en/ta/man/translate/figs-explicit]] and [[rc://en/ta/man/translate/figs-activepassive]])
Jesus commands the disciples to be ready for him to return the same way servants should be ready for their master to return. (See: [[rc://en/ta/man/translate/figs-simile]])
This refers to the door of the master's house. It was the responsibility of his servants to open it for him. (See: [[rc://en/ta/man/translate/figs-explicit]])