A wage determination sets the minimum hourly wages and fringe benefits you must pay workers on a contract, issued under the Service Contract Act for services or the Davis-Bacon Act for construction. It is tied to the labor category and the contract's location, so the same job can carry a different floor in different counties. Price your labor below it and you are noncompliant.

In a sentence

"This contract is subject to the Service Contract Act; the applicable wage determination is attached." That document sets your wage floor by labor category before you write a single price line, so pull it before you build your cost estimate, not after.