Instead of drilling in the earth for geological samples of rock and minerals, this kind of core drilling has to do with the interior, manmade landscape. Contractors and those in the A&D biz use the term core drilling to refer to the method of drilling holes in floors and ceilings to allow the installation of communication electrical lines. When there is no wall close enough and a power pole is just too unaesthetic for the application, core drilling is the answer. However, since you are most frequently having to drill into reinforced concrete, packed with miles of rebar, it is necessary to x-ray the floor as to avoid disaster. X-raying is expensive, and noisy core drilling has to be done after business hours as not to drive tenants insane, so the whole process is a bit more costly. One last warning: contractors tend not to install cores exactly where you drew them, and it’s not always due to sloppiness – structural integrity is a major factor. Drilling into a beam is not an option, and beams tend to be places where you least want them – it’s all part of Murphy’s Law.