The Tyler’s 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.
As an appointed officer of the Lodge, he is sometimes known as the "Outer Guard", sitting outside the closed door of the Lodge, armed with a sword.
The Tyler’s duties and principle role are to ensure that only those who are duly qualified are allowed to enter the Lodge. He guards against “cowans” and “eavesdroppers”. During the Middle Ages, a cowan was an uninitiated or non-apprenticed operative mason who built stone walls of poor quality.
While the Tyler is sometimes called upon to assist in the preparation of candidates, his chief duty is to (symbolically) keep unskilled workmen from overhearing any conversations within the Lodge that they are not qualified to hear.
After the Lodge members are inside the Lodge, the door closes and it is the Tyler’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 and gloves.
To be fully and properly dressed before entrance into the Lodge, the visitor must be wearing their apron over the top (on the outside) of their suit coat and the apron strings must be fully tied before the Tyler will allow the visitor entrance. Those present claiming to be visitors from another Masonic Lodge have to answer a number of questions to test their claim of actual membership in the Fraternity.