UNION – Get a grip!

It sounds a little crazy, but climbing walls is the latest rage that has hit Maine. Rock Rats Climbing Center on Route 17 opened Dec. 31 as Maine’s largest recreational facility for indoor climbing, according to co-owner Kerry Blake.

The sport is hot in the western United States and in big cities such as Boston, she said.

“There’s nothing like this in the area,” Blake said, noting that Portland has a smaller center with shorter walls called Maine Rock Gym. A few facilities, such as the YMCA in Rockport, have small climbing walls.

People of all ages can scale Rock Rats’ nearly 40-foot floor-to-ceiling walls with some basic training and the right tools. There are different walls for different skill levels.

The climbing center, located at 3357 Heald Highway, is housed inside a 40-foot-by-60-foot three-story steel building. The interior walls are made of steel beams and heavy-duty plywood covered with cement composite to give the appearance of rock.

Getting a grip takes on a whole new meaning when climbing indoors. The sport requires special climbing shoes, a harness, ropes, pulleys and a spotter, known as a belayer. The belayer catches a climber who loses his grip and assists those coming down from a climb.

Some 18,000 T-nuts embedded in the walls provide endless options for mounting “holds.” Holds are pieces of molded fiberglass that are gripped by hands or feet to climb the walls. Holds come in a variety of shapes and colors. On the children’s wall, the holds are recognizable shapes such as turtles, bats and seashells.

To get started, climbers can either rent or buy equipment. A pair of shoes can cost between $50 and $150 – the same cost as climbing harnesses. No special clothing is needed, just loose-fitting duds.

“You don’t want to wear tight jeans,” Blake, 36, of Warren, said.

The price to rent a full package – harness, shoes and chalk bag – is $5. The cost of day passes and monthly or yearly memberships varies by age. An adult day pass for weekdays after 3 p.m. and weekends is $15.

Blake and her husband, Jeff Blake, 39, have been climbing for many years.

“We’re both big climbers,” she said, noting they often use Camden Hills Park to enjoy the sport outdoors.

The sport offers full body exercise, using accessory muscles for balance.

“There’s not much in the area for teens and young adults to get physical activity,” Jeff Blake said. Climbing “promotes a healthier lifestyle. It’s a definite exercise.”

Indoor climbing can be a stepping stone to the great outdoors, Blake said. After mastering the basics indoors, those skills can be applied to rock climbing outdoors. Camden Hills and Acadia National Park have climbing spots.

Rock Rats plans to offer training in confined space rescue, a technique used last year at Dragon Products Co. in Thomaston to save a Cianbro worker who fell 52 feet in between a cluster of silos. In a related business, Maine Technical Rescue, the Blakes teach “high-angle rescue,” such as pulling people off cliffs.

In just a few weeks, Rock Rats has drawn attention from a diverse populace. Rock Rats has served climbers from age 4 to 57.

The 4-year-old “climbed and climbed and climbed and wore his dad right out,” Blake said.

Some local Boy Scouts have come to earn leadership points, a North Carolina company has inquired about its executives climbing for team-building skills, and 22 Pen Bay Christian School students showed up for a workout.

Rock Rats also is eyeing the possibility of area schools starting competitive climbing teams, she said. High schools in Fryeburg and North Conway, N.H., have such teams, she said.

For information, visit the Web site: www.villagesoup.com/rockrats.