Gillnets are normally rectangular, being much longer than high, with a float (or cork) line along the upper edge and a lead (weight) line along the lower edge. They are designed to be set vertically in the water. Fish do not apparently see them or, at least, are not deterred by them; they force their head through a mesh as far as it will go, only to find, in most cases, that their body is deeper than their head.
Tangle nets are similar to gillnets but are more loosely set, usually on the sea bed. They are aimed at entangling such prey as spiny lobsters and spider crabs, the spines of which make it almost impossible for them to detach themselves once caught. The role of the netting quality in terms of mesh size and material (e.g. whether monofilament or braided) is also relevant here.
Trammel nets, although they resemble gillnets, operate on a different principle. They are in fact two or three nets in one: one net with a fine mesh made of fine flexible (usually braided) twine is laid against another, or sandwiched between two others, of larger mesh and stronger thread.
Throw or cast nets are also exclusively artisanal gear. Usually circular in design, they are thrown, with considerable skill, over a fish school in very shallow water. The fish are trapped on the bottom and can be retained in the net as it is taken from the water by the fisherman.
