To put 2 lengths of gutter together, simply cut back the front bead / lip of the gutter 1" or
more depending on your needs. Do the same for the hem in the back if present. Cut where needed to create tabs.
Overlap the 2 lengths of the gutter and join them by
soldering if possible, or with
zip screws / rivets and
sealer if not.
Coupling pieces can be manufactured if needed. Keep in mind that using a coupling piece like a cover plate gives the appearance of 2 seams. Splice plates
can also be manufactured. Unlike cover plates, these sit on the inside of the gutter, giving the appearance of one seam, like overlapping 2 gutter lengths.