For a canopy, the Design prints show a "boundary weld" on toe of an angle, inside a frame, to metal decking.

I'm guessing it's like "boundary" nailing for wood diaphragms.  That would be the welding around the exterior of the canopy.  The interior nails/welds would be called "field" nails/welds.  Do they specify field welds?  It's got to do with the shear forces in the canopy acting as a horizontal diaphragm.