sentences:  He developed his Yosemite crack climbing skills by building and practicing on a wooden, adjustable crack machine.In Tuolumne Meadows above Yosemite Valley, Higgins teamed with Kamps, Vern Clevenger, Pat Ament, Chris Vandiver, Tom Gerughty and other partners to create new routes.He and others of the period stood on small edges and undulations, hammered with Rawl Drive drills to place quarter-inch bolts where necessary.