a saw carriage or module for manually , semiautomatically or automatically cutting stems typically supplied by a stem handling apparatus , which stem handling apparatus delivers full - sized , substantially tree - length stems to one or more of the saw carriages for cutting into logs , poles or other segments . during automatic operation of the module stems are typically scanned by an optical device and the physical characteristics of the scanned stem are sent to a computer , which selects the cutting pattern and transfers this information to a programmable logic controller . the programmable logic controller typically orchestrates positioning of one or more linearly - adjustable saw carriages or modules and on - board carriage saw blades to optimize cutting of the stems into the segments . after the modules and saws are so positioned , each stem is sequentially transferred by the handling apparatus to the saw modules , where it is positioned , clamped and cut into multiple segments at the preselected optimum points . stem segments are ejected from the saw carriages or modules by ejecting devices provided on each module .