1) A fishing or fowling net with three layers of meshes.
1416 noctant cum j tramell piscand’, Fulstone
1417 ‘one net called a Tramaill ... for taking fish in the dam’, Selby
1572 an olde nette with iiij tramel nets, Skipton
1741 fishing with a trammel, Horbury.
2) Of uncertain meaning.
Of uncertain meaning in some inventories: 1560 one acre of lande sawne with berlie, lyinge oof Tramelles, Knaresborough
1759 4 soals & Iron Tramels j Corn fork, Barnoldswick. The OED has 'shackles' as a contrivance to hobble an animal.