The scope is factory-zeroed, and requires minimal further zeroing to suit different users. The top of the scope has two perpendicular knobs for zeroing the sight. Zeroing weak references obviates the need to do this. Zeroing an mrad based scope is easy for users familiar with base ten systems. On modern hard-disk drives, zeroing the drive will render most data it contains permanently irrecoverable. The woodies had a three-part zeroing mechanism&colon; a lever, a lever stop, and a knob. It can also lead to unreliabilities when zeroing the gun. When it is constant, it is simply due to incorrect zeroing of the instrument. Using the zeroing blend mode, they can also be used as masking instructions. Lots of discussions went into zeroing in on a title for the movie. Most Swedish universities have some kind of "nollning" (""zeroing"") or "inspark" ("kicking-in").