CARLISLE, PA., AUG. 22 -- The Washington Redskins moved to shore up a thin defensive line this afternoon by acquiring holdout lineman Tim Johnson from the Pittsburgh Steelers for either a fourth- or fifth-round draft choice.

Johnson, 25, started 26 games the last two seasons and played every line position for the Steelers. He became expendable after a couple of young players had good camps, and when it became clear the two sides wouldn't be able to agree on a contract.

Redskins General Manager Charley Casserly first discussed the trade last Friday when the Steelers played at RFK. He agreed to give the Steelers a No. 4 or No. 5 choice, depending on how much Johnson plays this year.

He received permission to negotiate with Johnson, and on Tuesday reached agreement on a three-year contract believed to be worth about $1 million.

A 1987 sixth-round draft choice out of Penn State, Johnson is 6 feet 3, 270 pounds and a weightlifting fanatic, a quick player who is a very good run defender.

"He's a good, solid player against the run," Casserly said. "He should help our inside pass rush. He's real aggressive."

He probably won't start for the Redskins, but will be an inside pass rusher on passing downs. He could also play right end if Fred Stokes's shoulder doesn't respond to therapy.

At the very least, he is another quality player in an important area. Coaches and team officials have been concerned about their depth in the defensive line.

They're comfortable with starters Charles Mann, Tracy Rocker, Darryl Grant and Stokes, as well as pass-rushing specialist Markus Koch. But almost everyone else has been a disappointment. They apparently don't feel that Plan B signees Milford Hodge and Pat Swoopes, rookie Kent Wells or others had played well enough to provide insurance in case someone gets hurt.

"It feels pretty good," Johnson said after landing at Dulles tonight. "It's kind of hard when I realize that I won't be seeing my Steeler buddies everyday, but that's part of this business."

He had been working out on his own, adding: "I'm in pretty good shape, but after those two-a-days {Thursday}, I'll be one sore dude."

Steelers Coach Chuck Noll criticized Johnson for missing camp and said he might not have made the team anyway.

"I don't want people who don't want to be here," Noll said. "You can't have chemistry with those kinds of people when they miss training camp, and we did a lot of new things defensively. He was going to have a tough time making the team. I don't know if this sends a messasge of our {several} other holdouts; that's the way we do it." Rain Curtails Work

Coach Joe Gibbs ended the Dickinson College portion of training camp a day earlier than scheduled this afternoon when a second straight day of heavy rain kept them off the practice field.

The Redskins worked in a gymnasium this morning, then with no playing field available were dismissed after an afternoon weightlifting session.

They'll work twice Thursday at Redskin Park, where an artificial turf practice field allows them to practice under almost any conditions.

"We got a lot done this morning, but we can't get outside," Gibbs said.

Despite leaving camp a day early, Gibbs said the Redskins accomplished a lot of their goals.

"We're not where we want to be yet, but we worked hard," he said. "We had only one major injury {Reggie Branch's fractured ankle} and feel good with that. There were a lot of good things and some things we still need to work on."

After working twice Thursday at Redskin Park, the Redskins will have a walk-through Friday morning before the team's annual "Welcome Home" luncheon at the Grand Hyatt. They'll fly to Cleveland Friday afternoon, play the Browns Saturday and return to Redskin Park for practice on Monday. Jacoby Ready to Go

Tackle Joe Jacoby, who has had something of an amazing recovery from reconstructive surgery on his left knee, confirmed he'll make his 1990 debut against the Browns on Saturday.

"We'll see how it goes," he said. "It has felt good so far."

Line coach Jim Hanifan said he'd "play it by ear" in deciding how long Jacoby will play. "We'll get him out there in the second quarter for a few snaps," Hanifan said. "We'll see how it goes and how it feels. I don't want to overdo it."