As I stated in my Seneschal post, I talked about how I am always interested in their duties and etymology. Let us dissect this necessary post and his duties.
Merriam-Webster's dictionary defines Tyler as a person's name. Interestingly enough, they list "Wat the Tyler" as a notable name in history. In Mr. Robinson's book "Born in Blood" Wat is believed to an indication of possible Freemasons existing in the time of the Peasant's Revolt in 14th century England. In old English, a Tyler was thought to also be a doorman to an inn, early meeting places of Freemasons before they established their own buildings.
Now we can change the name slightly and see that a "Tiler" is someone who lays tiles. This is interesting as modern speculative Freemasonry pulls from positions and tools of the elder operative Masons that were known for their great accomplishments in history. We also look at the Entered Apprentice Degree where we see the symbolism of the checkered floor, that would have required a skilled tiler to lay.
In modern times, the Tyler serves to prevent non-members and impersonators from entering a private Lodge meeting. They also should serve on the Investigative committee for those Brothers who come to visit the Lodge along with the Senior Warden who also serves to verify the membership of everyone in the Lodge. He is also a face of the Fraternity and should always act accordingly.