The keel length of koch was about 10–25 meters (about 30–70 feet). It had 13 combination ribs, each consisting of several details. The keel was also a combination of several parts. Bulkheads divided the body into several cross-section compartments. Each compartment ("cherdak") served a specific purpose. There invariably were the fore-part compartment used as the crew's quarters, the stern cabin for the captain, and the cargo hold amidships. The koch had a flat deck. A typical koch carried one square sail on one mast. A distinctive peculiarity of the koch was the relatively big size of its square rudder fin which compensated for the special extra-slim design of the upper part of the rudder. This type of ship had two main anchors and, very often, light anchors. Naval historians think that the light anchors could have been used for mooring kochs to the edge of the ice fields.