Tool building is the process of constructing tools and machines for a variety of purposes. The term 'tool building' can refer to the construction of physical tools, such as hammers, saws, and drills, or it can refer to the construction of virtual tools, such as software programs. In this crossword, the solution for the term 'tool building' is 'SHED, ' which is a structure used for storing tools and materials. A SHED is typically a small, single-story structure with a roof and walls made of wood, metal, or plastic. Sheds are often used to store gardening tools, lawnmowers, and other outdoor equipment.