(From USA Today)—The gray-haired men arrive promptly at 8 a.m. and walk to a small room in the back of the office.

They put down their briefcases and begin unpacking tools from another age: A wooden ruler. A protractor. Dog-eared reference books with titles like "Machinery's Handbook" and "Steel and Wire."

The men are retired engineers who spent careers building jets and trains and cars. Now they're back, working several days a week at Supply Dynamics in Loveland, Ohio.

They don't look much like revolutionaries as they sit quietly, studying blueprints. But these engineers, along with millions of other older workers, are changing the culture of the American workplace.

Nearly one in five Americans over age 65 is now in the labor force—the most in about 50 years.

Older workers are coming back because they need the money or don't feel ready to retire, and because businesses are increasingly willing to pay for the know-how they bring to the job.

"There's no substitute for experience," said Trevor Stansbury, Supply Dynamics' president. "They bring a wealth of knowledge."

Stansbury also has found the engineers he's hired bring a more subtle cultural change to a workplace filled with colleagues young enough to be their children, or grandchildren.

Like the tools in their briefcases, their approach to the job is rooted in another time.

They are less likely to use social media inside or outside the office, and they are less interested in work activities unrelated to their assigned tasks.

Most have never seen a "theme day," for example, in which everyone wears wacky neckties or competes to make the coolest invention entirely out of duct tape. And the idea of going to the gym or playing Nerf basketball during lunch breaks is as alien to them as a shift-change whistle would be to their younger co-workers.

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