His Jewel is the Sword, by which he symbolically refuses entrance to anyone who is uninitiated in the Craft. The sword has no scabbard, as it is his symbolic duty to always have his sword drawn, ready for the defense of his post.
The Tiler's duties and principle role is to ensure that only those who are duly qualified are allowed to enter the Lodge Room. While the Tiler is sometimes called upon to assist in the preparation of candidates, his chief duty is to (symbolically) keep unskilled workmen from overhearing the conversation within the Lodge Room.
After the lodge members are inside the Lodge Room, the door closes and it is the Tiler's duty to decide whether late arrivals may enter. It is also his duty to make sure that each visitor is "properly clothed", which means they must be wearing their Masonic apron.
The Tiler's position is similar to that of a Supervisor. The Tiler (or Tyler) of a Masonic Lodge is an elected officer of the Lodge.