We are famous for our Lobstah (Lobster for you non NE Folks) Rolls and these are the ones used for those. They are much easier to toast as well. I be from Joisey originally IIRC we had that type as well.
Heres what I found on Wikipedia
There are two basic types: top-loading, which are available only in New England and called Frankfurter rolls, New England Style Rolls or Lobster Buns in some areas, and side-loading, common in the rest of the United States also called American Style Buns. The advantages to a top loader are that it holds the hot dog securely and fits nicely into little three-sided paper boxes. Top loaders are generally baked side by side and torn apart as needed, leaving a flat side surface for grilling.