With this smack-your-forehead, it’s-so-obvious, single-flag configuration, there’s no measuring the exact distance between where the clips will be applied to accommodate flags with varying spaces between their grommets. It’s a simplistic approach that works well in light conditions for shorter periods of time.
Make sure the halyard line will be the right length, and tie a small carabiner onto each end. Before raising the pole, tie on a third carabiner to the top and clip the middle of the halyard through it. The clips on each end of the halyard attach to each of the two grommets of the flag forming one continuous loop with the flag itself joining each end of the halyard.
There’s one, important point to remember! The halyard by itself does not form a continuous loop unless the clips are linked together. This means, when the flag is not attached, if one end of the line happens to get pulled upward past arms reach, there’s very little likelihood it can be retrieved without lowering the whole pole. So, after the pole is raised, whenever the flag is not attached, always remember and be careful to join the two clips together!
The following text is by Adolph E. Peschke as presented in the 1998 printing of the 1993 edition of the Pioneering Merit Badge Pamphlet:
This knot has the reputation of having a firm, sure grip once it is put under pressure. The multiple opposing turns provide friction and put a bend in the standing part of the rope, which becomes more difficult to pass through the turns as a lateral pull is applied. The prusik is widely used by mountain climbers as they attach a loop (grommet) made from a smaller rope to a larger rope to form a hand or foothold. It can also be used to form hand and shoulder loops for a lateral pull on another rope or to drag a log or spar. Pioneering Uses
To hook a light tackle on a vertical or horizontal spar.
To make hand and foot loops for climbing another rope or vertical spar.
To make hand and shoulder loops as an aid to hauling a large log. It can easily be moved along as the positions require.
To provide the grip and a loop to tie another line with a sheet bend.
To provide a safety brake against back-slipping on a load-lifting line. (Do not use when lifting a person.)