For this barn door, you need long lengths of 5 mm (3/16 in.) wooden dowel.
It is easily cut to the lengths required with a small cheap hacksaw.
Note: The length of bought dowel can be somewhat inaccurate. So if you have bought 2.4 m lengths of dowel, you might have a couple of centimeters less than you bargained for! Hence I cut my 120 cm spars from 1.8 m lengths of dowel.
Now there's a little work to be done on the horizontal spar. Use 20-pound flying line if you have some, otherwise just use some of your 50-pound flying line. With this kite laying on the floor, each tip of the horizontal spar will be 0.08 DL (9.6 cm, 3 3/4 in.) above the floor.
The remaining steps:
After the bridle has been made up, one line connects to where the spars cross, with a Lark's Head knot. This is shown in closeup in the bottom photo.
As mentioned earlier, there's more kite making on this site than you can poke a stick at. :-)
Want to know the most convenient way of using it all?
The Big MBK E-book Bundle is a collection of downloads—printable PDF files which provide step-by-step instructions for many kites large and small.
That's every kite in every MBK series.