Establish the location for a fence, and gather information needed to ensure that there are no electric cables or water lines in the area. Align posts, using lines or by sighting, and verify vertical alignment of posts, using plumb bobs or spirit levels. Measure and lay out fence lines and mark posthole positions, following instructions, drawings, or specifications. Dig postholes, using spades, posthole diggers, or power-driven augers. Set metal or wooden posts in upright positions in postholes. Discuss fencing needs with customers, and estimate and quote prices. Mix and pour concrete around bases of posts, or tamp soil into postholes to embed posts. Make rails for fences, by sawing lumber or by cutting metal tubing to required lengths. Nail top and bottom rails to fence posts, or insert them in slots on posts. Stretch wire, wire mesh, or chain link fencing between posts, and attach fencing to frames. Attach fence rail supports to posts, using hammers and pliers. Assemble gates, and fasten gates into position, using hand tools. Complete top fence rails of metal fences by connecting tube sections, using metal sleeves. Insert metal tubing through rail supports. Attach rails or tension wire along bottoms of posts to form fencing frames. Nail pointed slats to rails to construct picket fences. Construct and repair barriers, retaining walls, trellises, and other types of fences, walls, and gates.