A downhole drilling apparatus for interconnection in a casing or liner string having a drill bit disposed thereon for enabling the drilling of intersecting wellbores without removal of the drill bit is disclosed. In a disclosed embodiment, the apparatus comprises a housing having a window. A whipstock...http://www.google.com.au/patents/US6374924?utm_source=gb-gplus-sharePatent US6374924 - Downhole drilling apparatus
