When at work, the finger you use when pointing to the "pet" person or "ass kisser" to whom you generally assign the easiest tasks, indicating that they are your bitch.
When a guy has really lady likefingers he is said to have bitch fingers, implying that he is either a fag who moisturises or hasn't done a day's work in his life. Bitch fingers are common among piano players (but not compulsory).