The Dovetail Bed (also called Tooling Plate or Fixturing Plate), has a pattern of M4 threaded holes which can be used to screw stock down directly, or with toe clamps to fixture work. 

The dovetail slots are used to hold vises, rotary axes, and other quick-connect fixturing. 

The bed is normally fixed in place the same was as the print bed - the magnetic latches pull the bed pins down into the pin holes. It is also possible to affix the bed more rigidly by threading an M3x25mm screw (with washer) through the hole next to the pin and into the bed support bracket: