In Maryland, the Grand Master has the power to make a Mason at sight. He does not just tap him on the shoulder or issue him a certificate. He confers all three degrees in one day, with himself in the chair (or at least in the room) without any requirement to show proficiency.
There are actually two ways in which conferrals at sight have been done. The first was done by GM Thomas J. Shryock around the turn of the 20th century. The candidate was a prominent clergyman. The GM summoned the officers of the Grand Lodge to meet at the Masonic Temple on a certain day at which time all three degrees were conferred in full form, GM in the chair. At the conclusion of the MM degree, the candidate was an unaffiliated Master Mason. He then put in a petition to a local lodge, was investigated and voted on, after which he became a member of that lodge by affiliation.
The second method, also used by GM Shryock, was that a lodge holding a petition which they had investigated and voted on, petitioned the GM to make the petitioner a member at sight due to his extensive public and professional duties which did not allow him time to follow the normal course to membership. Accordingly, a special meeting of the lodge was held starting in the early afternoon, the GM (and a number of guests) attended, GM took the chair, and he and the lodge officers conferred all three degrees (with dinner between the 2nd and 3rd), after which the candidate was a member of the lodge like any other newly raised brother.
This second method was used several years ago for a young man in the military who had petitioned and had been investigated and voted on but who had received orders to deploy to Afghanistan within a couple weeks. At the request of the lodge, the GM was pleased to take the GL officers to a special meeting of the lodge and made the man a mason at sight as above.