The most convenient shape for the rods is square, as fitting the corners and taking tacks most easily.  The sectional size of the rods is governed by the dimensions of the kite, and to a certain extent by the number of stretchers used.  If four stretchers are employed in each box, two near the top and two near the bottom, the rods need not be so stout as in a case where only a single pair of central stretchers is preferred.

Lay the two boxes flat on the floor, in line with one another, and the joins at the same end.  Pass two rods through, and arrange the boxes so that the outer edges are 1/2 inch from the ends of the rods. (These projections protect the fabric when the kite strikes the ground).

Lay the rods on one corner, so that the sides make an angle of 45 degrees with the floor, pull the boxes taut—­be careful that they are square to the rods—­and drive three or four tacks through each end of the box into the rods.  Then turn them over and tack the other sides similarly.  Repeat the process with the other rods after measuring to get the distances correct.

The length of the stretchers is found approximately by a simple arithmetical sum, being the square root of the sum of the squares of the lengths of two adjacent sides of the box.  For example, if each box is 20 by 15 inches, the diagonal is the square root of (20 squared plus 15 squared) = square root of 625 = 25 inches.  The space occupied by the vertical rods will about offset the stretch of the material, but to be on the safe side and to allow for the notches, add another half-inch for small kites and more proportionately for large ones.  It is advisable to test one pair of stretchers before cutting another, to reduce the effect of miscalculations.

The stretcher notches should be deep enough to grip the rods well and prevent them twisting, and one must take care to have those on the same stretcher exactly in line, otherwise one or other cannot possibly “bed” properly.  A square file is useful for shaping the notches.

Ordinarily stretchers do not tend to fall out, as the wind pressure puts extra strain on them and keeps them up tight.  But to prevent definitely any movement one may insert screw eyes into the rods near the points at which the stretchers press on them, and other eyes near the ends of the stretchers to take string fastenings.  These attachments will be found useful for getting the first pair of stretchers into position, and for preventing the stretchers getting lost when the kite is rolled up.

The bridle is attached to four eyes screwed into the rods near the tops of the boxes. (See Fig. 118.) The top and bottom elements of the bridle must be paired off to the correct length; the top being considerably shorter than the bottom.  All four parts may be attached to a brass ring, and all should be taut when the ring is pulled on.  The exact adjustment must be found by experiment.  In a very high wind it is advisable to shorten the top of the bridle if you have any doubt as to the strength of your string, to flatten the angle made by the kite with the wind.