Weir's two-round score of 7-over par and Ames's 6-over par were just good enough for both players to remain in the tournament. The 36-hole cut, which includes all players within 10 shots of the lead, was 8-over par.
Defending champion Retief Goosen, Olin Browne and Jason Gore share the lead at 2-under par heading into Saturday's third round. K.J. Choi and Mark Hensby are tied for fourth at 1-under par.
Vijay Singh (even par), Sergio Garcia (even par), Jim Furyk (1-over) and Tiger Woods(1-over) are among the notables within striking distance near the top of the leaderboard.
Mike Weir of Bright's Grove, Ont., strikes a tee shot during Friday's second round of the 105th U.S. Open. (AP Photo/Ann Heisenfelt)
Weir of Bright's Grove, Ont., shot 2-over par 72 on Friday and finished Thursday's opening round with a score of 75. He struggled early in his second round, firing four straight bogeys on the back nine.
However, the 2003 Masters champion improved in the afternoon, draining three birdies to make the cut.
Calgary's Ames shot a five-over 75 Friday but still managed to advance on the strength of his opening-round score of 71.
The tournament came to an end for two other Canadians. Ian Leggatt of Cambridge, Ont., and David Hearn of Brantford, Ont., each failed to make the cut.
Leggatt shot a 76 Friday for an 11-over total, while a round of 79 left Hearn at 16-over par.
American Ryder Cup captain Tom Lehman (9-over), Padraig Harrington (11-over) and Chris DiMarco (13-over) were among the notables who failed to move on.
with files from Canadian Press
