37 Repairing, maintaining and servicing engines, tractors, motor graders, loaders, tractor-scrapers, off-highway trucks, fork lift trucks and similar carriers, straddle carriers, log skidders, pipe layers, electrical generating sets, compressed air equipment, irrigation pumps, cranes, excavators, and parts therefor; laying out, construction supervision and installation of shelving and storage facilities; repairing, maintaining, and servicing air-driven tools, backhoe loaders, articulated dump trucks, dump trucks, paving equipment, compactors, wheel dozers, forestry machinery, namely, mechanized tree harvesters, forestry machinery, namely, mechanized tree processors, and parts, attachments, and accessories therefor