A cheap way to make a hog trap is make a circle with t-posts and then put the cattle panels up on the t-posts. The last cattle panel should overlap the first panel that you set by several feet. Do not secure the end of this panel, but put a door spring from the end of the panel to somewhere on the first panel. The hogs will push against the panels and find their way into the pen and the spring will pull the panel back closed and they can't get out.
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U.S. Army Military Police (ABN) 1998-2003