These are usually 4 mm between legs and are
often used for the assembly of frames.
I have also used this type to attach rim pieces to crown boards.
I also have used them for fixing the side panels on frame feeders
Often 10 mm or 12 mm between legs these are
available in many leg lengths and wire sizes. The thinnest type,
with legs in the region of 10 mm length, are suitable for the attachment
of mesh to wooden components.
Long legged and coarse wire versions can be used for box making.
To enable magazine loading this shape of nail was
developed. They are effective but relatively expensive when
compared to traditional types of nail. The cost may be offset by the
comparitively quicker assembly that they afford.