In the 1924 Willamette Iron & Steel Works Repair Parts Catalog, under the section "Operation of the (Steam) Engine," the first paragraph states, "The engine must be well secured to a substantial sled of liberal size.  Carefully prepare the setting so that the engine will have the best possible foundation."  These sleds were used to support the steam engine as it literally pulled itself in and out of canyons, across streams and along ridges to the next logging site.