The Washington Redskins have locked down a big piece of their offensive line.

Tackle Trent Williams has agreed to a five-year contract extension worth $66 million, a source told FOX Sports 1 NFL Insider Mike Garafolo. The deal includes $43.25 million in guarantees.

Williams, the No. 4 overall pick in the 2010 NFL Draft, is a three-time Pro Bowler and has 70 career starts under his belt.

More from FoxSports