RICHMOND, Va. -- Washington Redskins offensive line coach Bill Callahan looked at the film and, over the years, noticed defensive linemen getting lower in their stance. It made life tougher for offensive linemen. Then he considered how the NFL's the collective bargaining agreement limits the offseason work his players can do. That too made life tougher.

So he decided to do something about it this offseason -- and it could be a reason the Redskins' line develops in 2019. If nothing else, Callahan can add "sled designer" to his list of career accomplishments. Sort of.

Callahan wanted to modernize blocking sleds, so he called Hans Krause, the president and owner of the Rae Crowther Co. and someone Callahan has known for about 20 years.

They had exchanged ideas in the past, and Krause, whose company is based in Rock Hill, South Carolina, visited Redskins Park this offseason to get a sense of what Callahan wanted. They measured the angles and height of a defensive player, wanting to know how his weight was distributed when he came off the ball. They used stubby arms to force offensive linemen to keep their hands tight.

After the initial design, Callahan offered suggestions for more tweaks. Then Krause, whose family began designing sleds in 1932, came up with the finished product.

The new sled has been a key part of the Redskins' line work during training camp. They'll use it before practice and sometimes after; they'll use it when linemen come to work out. Callahan and Krause say the sled provides instant feedback. Indeed, at a recent workout, one lineman struggled to lift the sled in the same fashion as three others there that day.

"We want the person to fail a certain amount," Krause said. "If you're not good in a game, you shouldn't dominate the sled. The better the sled, the more feedback you get from it. Bill's always an innovator. He's that kind of guy. Some don't question it; they just use whatever's in the market."

The Redskins have been among the most injured groups in the NFL over the past two years and have used 70 different offensive line combinations -- some of which were only for a snap. They are the only team using the sled they've dubbed "The Climber" and view it as another tool to maximize player development.

"It's hard to simulate those blocks when working in a group, and it's hard to go against a defensive line all the time," Callahan said. "It's a really good offseason device, a good in-season device and it's perfect for training camp where they can focus on their fundamental technique."

Callahan said the sled mimics a defensive linemen's stance and leverage points upon contact. The sled is heavier at the base -- it weighs about 320 pounds -- and contains shoulder pad chest plates so an offensive lineman has something to grab. The arms are shortened, but they could be lengthened in future adaptations. The goal for an O-lineman: Get into the chest plate pads, lift it and climb and close the distance with the defender. It forces them to work their feet and hips. Callahan said it allows them to simulate various blocks.

Callahan also edits practice film to occasionally show how using the blocking sled correlates to their on-field technique.

"There's a direct correlation," he said.

It didn't take long for his players to see an impact.

"The first time I did it, I said, 'This is the most realistic thing we're going to do,'" Redskins guard Brandon Scherff said. "[Callahan]'s always trying to ask you how you can improve it. It's perfect."