Any vessel over 150 feet in length has to have a forward
running light that indicates it is over that length. Most of these
have a fore-mast that holds the running lights. There are other lights
on the mast as well. The lights indicate many things about vessel besides
her length. It can also provide other vessels with information like the type
of work they are doing like dive jobs or towing or even fishing. Sail boats
have a certain light arrangement also. At night it is necessary to make sure
that the running lights are working.