Stereo & Electronics - Alternator clock position?

Was looking to upgrade my alternator, and came across the term "clock position". Can anyone tell me what it means?

basically wehre the bolt holes on the casing are lined up ( you want to clock it untill the bolt holes are in eactly the same position as the stock alternator)

jimmy

Exactly the front case has the mounting holes & the rear case hase the output lug & regulator connector.
The have to be clocked right in order to fit in the car.