Solder subsequently participated in his first practice Thursday.
"It was great. It's been a while," Solder said of practicing, while noting the difference between college and the NFL. "There are some great players out here. It's a challenge definitely."
The Patriots did not disclose terms of Solder's deal, but a league source said it is a four-year contract, which is standard for first-round picks.
Solder, the 17th overall pick in the draft, was the Patriots' lone unsigned selection. He had missed the first seven days of training camp.
"I just had to stay in shape and study what I had been taught on the plays beforehand," he said.
Solder is a 6-foot-8, 319-pound converted tight end. He moved one spot inside on the offensive line early in his career and ended it as a first-team All-American lineman last year at Colorado. He was also a finalist for the Outland Trophy, awarded to the nation's best interior lineman.
"He's big, he can run, he's a good pass-blocker, he's a good run-blocker," Patriots coach Bill Belichick said earlier Thursday. "He plays on his feet. He's long."
The Patriots re-signed veteran Matt Light to continue to be the starter at left tackle, but he knows that the Pats might have found his eventual replacement.
"Drafting a guy that will come in and fill in for these old bones, it was inevitable," he said Wednesday. "Hopefully we'll have some fun teaching him a thing or two out here."
The Patriots could put Solder on the other side of the line and get him playing right away, but Belichick said the plan is still to keep Solder on the left side behind Light.
"That's what he played. And he played it well. That's why we drafted him. But can he play right tackle? I think he has the skill set to, but we'll see," Belichick said. "Eventually, everybody is going to have to block big guys, fast guys, quick guys, games, blitzes. Everybody will get tested sooner or later."
Mike Reiss covers the Patriots for ESPNBoston.com. Information from The Associated Press was used in this report.