For Keefer, 25, of Chambersburg, Pa., and his companions, Adam Henry of Chambersburg and Donna Maines of Williamson, Pa., Sunday is caving day. This day, it's a relatively easy piece of spelunking in a cave in Southhampton Township in Franklin County.
From the outside it's a jumble of rock slabs, the entrance a cleft about two feet wide and perhaps a dozen feet high. Within a few feet of the entrance, past a stone column and over a few boulders, it would be pitch black except for the lamps shining from their hard hats.
A bit farther along, everyone is on their hands and knees, crawling through a tunnel about as wide and wet as a small drainage culvert. Eventually, the passage widens out to where they can stand up again and the trio ascends into a large vault.
"This one has a lot of graffiti in it, which we don't like," Keefer said before entering the cave. Looking into the circle of light as a flashlight plays across the wall, one can see a fraternity's Greek letters emblazoned on it.
Water drips constantly from the ceiling and the cave floor is slick with mud. Everyone is covered with it before the excursion is over.
There are stalactites and stalagmites reaching down from the ceiling and up from the floor, occasionally meeting in a column. Rippling curtains of stone decorate the walls, formed by eons of mineral-rich waters dribbling over the rocks.
"Bat on your right, about shoulder level," Henry said as he led the way through a high, but narrow passage.
"That's about eye-level for me," said Maines, his fiancee. She gets low and to her left, giving the bat as much room as possible.
Their wings folded up and in hibernation, the bats are smaller than mice.
Through some more tight squeezes into another vault, they pick out the driest rocks they can find and sit down for a break. They set up a few candles to save on batteries.
"You need at least three extra light sources," Henry said. Helmets are also a necessity, since occasionally banging one's head into a rock comes with the territory.
Climbing boots, ropes, water, snacks and a survival blanket to treat or prevent hypothermia are also recommended.
Henry, 21, said he began caving about three years ago when Keefer introduced him to the sport.
"He just mentioned it to me one day and I said, 'Yeah, let's go,'" said Henry, a delivery man for Harmon's Furniture in Chambersburg.
Keefer has been cave crawling for six years. It was friends from the Tri-State Grottos, a caving group in the Hagerstown area, who got him hooked.
"I was a little claustrophobic at first ... then it was like a bug bit me," said Keefer, a molder at T.B. Woods in Chambersburg.
"They led me into it," said Maines, who works at Staples. She said there are caves in Williamson but, until a few years ago, she confined her explorations to the entrances.
"It's probably the factor of being somewhere different. You don't know what's in store for you," Henry said when asked why he enjoys caving.
When exploring an unfamiliar cave, Henry said a ball of string is important to be able to retrace the way back to the entrance.
"Never go into a cave with less than three people," Keefer said. If one person gets hurt in a fall or other accident, someone can stay behind while the third person goes for help.