Before any strange and unknown visitor can gain admission into a Masonic Lodge, he is required in the United States of America to take the following oath:
I, A. B., do hereby and hereon solemnly and sincerely swear that I have been regularly initiated, passed, and raised to the sublime Degree of a Master Mason in a just and legally constituted Lodge of such; that I do not now stand suspended or expelled; and know of no reason why I should not hold Masonic communication with my Brethren.
It is called the Tiler’s Oath, because it is usually taken in the Tiler’s room, and was formerly administered by that officer, whose duty it is to protect the Lodge from the approach of unauthorized visitors. It is now administered by the Committee of Examination, and not only he to whom it is administered, but he who administers it, and all who are present, must take it at the same time. It is a process of purgation, and each one present, the visitor as well as the members of the Lodge, is entitled to know that all the others are legally qualified to be present at the esoteric examination which is about to take place. This custom is unknown in English Freemasonry.
the source: Mackey’s Encyclopedia of Freemasonry