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There are 3 described basic methods of creating a split tongue. scalpel (cold steel), cautery (electric or laser), and tie-off. Scalpel and cautery methods are performed by a surgeon, but the tie-off method can be performed by anybody.
The tie-off method was developed by 19 year old Dustin Allor in which he took fishing line tied through an existing tongue piercing and looped it over the tongue tip. Over time, the fishing line is sequentially cinched tightly through the tongue tissue. This slow process (days to months) allows the tongue to heal as it is being split negating the need for stitches or cauterization due to nominal bleeding.
A split tongue can also be reversed, though more painful than creating it.
More can be read about split tongue on Wikipedia.
Needless to say, this procedure is NOT covered by insurance... but reversing it potentially can be covered by insurance.