<P> Half - mast or half - staff refers to a flag flying below the summit on a pole . In many countries this is seen as a symbol of respect, mourning, distress, or, in some cases, a salute . Strictly speaking, flags are said to be half - mast if flown from ships and half - staff if on land, although not all regional variations of English use "half - staff ." </P> <P> The tradition of flying the flag at half - mast began in the 17th century . According to some sources, the flag is lowered to make room for an "invisible flag of death" flying above . However, there is disagreement about where on a flagpole a flag should be when it is at half - staff . It is often recommended that a flag at half - staff be lowered only as much as the hoist, or width, of the flag . British flag protocol is that a flag should be flown no less than two - thirds of the way up the flagpole, with at least the height of the flag between the top of the flag and the top of the pole . It is common for the phrase to be taken literally and for a flag to be flown only halfway up a flagpole, although some authorities deprecate that practice . </P>

When do you fly the flag half mast