Fuente: WIPO "honey" Disclosed is a core drill guide apparatus for providing a guide for a core drill apparatus to drill into a substrate to form a removable core. The apparatus includes an elongate body with an outer surface and inner space, having an entrance end, an exit end and side walls, a distance between the ends defining a length or height of the elongate body and a width. An passageway extends through the elongate body from entrance to exit end, adapted so that in use, it provides sliding receipt of a fastening system to clamp the apparatus to an outer surface surrounding a first hole in a substrate, allowing the apparatus to abut the outer surface and drill out a core in the substrate underneath and surrounding the first hole. A corresponding guide method and fastening system are also disclosed.