Season 4 begins with Cowboy asking Eugene and Spencer to fortify his compound in preparation for the end days. Included: The guys construct a wood still to make sure that their neighbor will have fuel no matter what.

Cowboy convinces Eugene and Spencer to embark on an expedition for gold, but they encounter an interloper who threatens to steal their treasure.

Eugene and Spencer decide to build a solar-powered hot water heater out of salvaged pipes and old beer cans, but first they need to construct a chainsaw chopper for their friend who has the supplies they need.

The guys hunt for treasure using a metal detector made by Eugene out of bamboo, wire scraps and a salvaged transistor radio.

The guys rid a friend's home of honeybees and decide to start their own honey-making business.

The guys build a wood kiln out of discarded oil barrels and a huge outdoor rotisserie for cooking chickens.

Eugene and Spencer build a trickle-feed irrigation system using bamboo and some scrap metal in hopes of resolving a water feud that is threatening Cowboy's crops.

The guys transform a herb-drying shed into a guesthouse cabin for Spencer's visiting mother-in-law.

When Eugene breaks his mom's rare burl wood bowl, he and Spencer must cut down a giant burl, forge woodworking tools from scrap metal, and repair an old truck just to use the axle as a wood lathe, for turning their burl into a new bowl for Mama Gene.

A creek blocks the best route from Cowboy's house to the holler, so Eugene and Spencer build an old fashion swinging bridge from scavenged rope and hand-hewn bamboo. Will their hillbilly rope bridge hold weight? Or will it dump the boys in the drink?

Eugene and Spencer aim to clear an overgrown field and find a valuable item Cowboy hid there years ago. But their hand-made brush axes can't cut the dense growth, so the boys build a brush hog out of Cowboy's old truck and a couple of used lawn mowers.

The boys must come up with a contraption that can help notorious old moonshiner, Charlie Shine, bring heavy supplies to and from his hidden still. They'll construct a mechanical cable climber to take the load off Charlie.

Eugene and Spencer salvage a rusted-solid Winchester M37 and an antique hit and miss diesel engine from a barn full of scrap. They must make an electrolysis bath to strip the rust off the shotgun, which they'll trade for parts to restore the engine.

Spencer and Eugene set out to build a fish farm. But when they can't afford the cattle-watering troughs where they planed to put their trout, can they rig up their own fish tanks from nothing but a roll of plastic tarp and some old hay bales instead?

Widowed Mavis has doctor appointments to keep, and a stalled car. If the boys make a tire patch, a replacement gasket and a temporary fan belt out of junk, then they get an old alternator from a junkyard, they might get Mavis to the doctor on time.

Spencer and Eugene have two days to forge 15 knives for a collector. The boys construct a water wheel to power a homemade hydro-powered grinder—and to power an electric light. Because if they want to meet that deadline, they must pull an all-nighter.

Spencer and Eugene must build their own hillbilly houseboat, out of a discarded camping trailer, which they float on a pontoon platform made with rows of airtight oil drums, when Cheyenne gets a leisure boat and becomes a bit too big for his britches.

Eugene and Spencer plan to build wood-burning stoves out of steel barrels, with windows made of high-quality block mica. Can they also build a hand-powered pump trolley out of junkyard scraps for bringing heavy sacks of mica down from the mountains?

Spencer and Eugene must build a barn wood display case for Cheyenne's store. But to get the wood they must make traps to catch a critter, to make into groundhog grease, to trade for a dog, which they can trade for barn wood to finally make the case.

Mama Gene steps in a gopher hole and breaks her foot, leaving her homebound on the porch. She's plagued by insects, and missing out on the 4th of July festivities. So the boys build her a flame roasting bug zapper, and a hillbilly ninja rocket wheel.

Eugene and Spencer run out of vintage high carbon steel, for forging knives to fill an important order. Can they build a salvage barge from junk, to seek a lost sawmill in an abandoned underwater town, and retrieve the old steel that was left behind?

Eugene and Spencer need to turn a riding mower engine into an outboard motor strong enough to power a salvage barge. The boys want it to locate a lost sawmill in an abandoned underwater town, where they hope to retrieve any vintage steel left behind.