Although structured cabling has been around for over 25 years, the subject is becoming increasingly complex, and the original idea of unified cabling for all services is evolving. This also means that subfields such as data centers or industry, while integrated into the IT infrastructure, establish completely independent, specific rules. Along with topics like grounding and shielding, installation quality, or new trends such as 25/40-Gbit and single-pair Ethernet, PoE/PoDL, etc., it is becoming increasingly difficult for users to read and apply standards optimally and correctly. The authors are experts actively working in the fields of research, teaching, standardization, planning, and evaluation related to structured cabling and adjacent topics. They consolidate their knowledge here and present a guide to information technology in buildings.