use 3 16' cattle panels
t posts every 4 ft
4 10 gauge wire ties on each pole
and a swing door with a spring so once it triggers more can push in.
drop doors can be made of wood and are cheaper but you can only catch once no more can push in.
for your trigger use heavy braid line, atached to the door run through 1" steel rings, not pulleys, run it around the sides to the back of the cage and then tie on a thin piece of single strand wire from the braid to one of the T posts at least 12" above the ground. they break the thin wire to trigger the door.
you can use trees but due to shape they make it easier for the pigs to root under the edge of the cattle panels and lift them.
If you have lots of small piglets line the bottom 2 ft of the cattle panel on the inside of the trap with chicken wire.
This post was edited on 12/6 at 11:04 am