Tom's move is a trick that enables a player to breakthrough a second ladder. Its name originates from player Tom239 who devised it during a game (against dj11, on 15 December 2002) on Playsite. This was not its first use ever, just how it came to be known among hex players on Playsite.
In this diagram Red wants to connect to the bottom edge.
He pushes the ladder until he is right underneath it, and then he plays at 5.
Now Red´s two pieces at g3 and f4 are connected to the bottom edge via edge template IV2b, and his ladder can thus connect to the bottom edge in two different ways, by playing in either of the starred cells.