Canter infeed tilt and slew positions the log to the correct position, in relation to the canter bottom head. 

If the log "sawing" bottom face is skewed to the canter bottom head in the infeed, the infeed tilts and offsets to align the log bottom with the bottom chipping head.  The infeed then slews (moves vertically) as the log is processed through the bottom head.
If the log bottom is parallel to the bed line but offset from the bottom head, the infeed offsets only to align the log to the bottom head. 

Used on double length infeeds (DLI), optimized length infeeds (OLI) and single length infeeds (SLI).