600s: Applied Sciences and Technology
This week and next week are extra tricky as we explore 500s (Natural Sciences) and 600s (Applied Sciences). Why? Horses pop up in 590s (wild) and 630s (farming)---and, if you recall from last week, 798 for equitation and racing. Engineers (620s) might need mathematics (510s), physics (530s), or buildings (690s), if not architecture (720s). Gardeners might look through the 590s for animals in your garden, 580s for botany and wild plants, and 635 for horticulture and gardening.
How to keep them straight? If it is a natural science, especially the theory of math or a science, go with 500s; if it is used or does something, try the 600s.
Here is a roadmap of Applied Sciences and Technology:
610s: Medicine (including diets, exercise plans, or specific symptoms/ailments)
620s: Engineering (including guns, automotive repair manuals, wind generators, RV maintenance, or knots)
630s: Agriculture (farming, raising livestock, gardens, dogs and other pets)
690s: Buildings (drywalling, plumbing, adobe or straw-bale or frame construction, greenhouses, outbuildings, flooring, tile, and painting)