What are the duties of the Tyler in a Craft lodge?

The Tyler's principal duty is to guard the door of the lodge against intrusion 12 and to look after the door [grandlodgeofindia.in]. He guards the lodge room from the outside [ugle.org.uk]—the outer door—to ensure that the sacred precincts remain covered and secure 2.

To fulfill this role, the Tyler is entrusted with guarding the entrance to the lodge room and ensuring that only duly qualified Masons are allowed to enter [rglni.org]. In modern practice, he uses the Tyler's sword to challenge anyone seeking entry and to verify their qualifications [rglni.org]. Traditionally, the Tyler's sword was wavy in shape—in allusion to the flaming sword placed at the east of the Garden of Eden—and was kept drawn without a scabbard so as to remain ever ready for defense 2. Operative lodges appointed this guardian because tile layers completed and secured buildings from intrusion 12; historically in early Scottish lodges, the youngest entered apprentice filled this role as the lodge officer 4.

Beyond guarding the entrance, the Tyler is the first person a Candidate for Initiation encounters during the ceremony [ugle.org.uk]. Outside the door, his responsibilities include helping to prepare candidates and allaying their nerves before they enter the lodge [ugle.org.uk]. In formal processions or public ceremonial retirements, the Tyler leads the way bearing his sword 3.