Tibetan block-letter script (gzab ma), generally known as the headed, dbu-can [pron: "u-chen"] script, is traditionally written using a hand-made bamboo or reed pen cut at an angle. A broad steel nibbed italic calligraphy pen may be used instead. Steel nibbed calligraphic pens designed for left-handed writers of Roman italic script are slanted at a suitable angle for a right-handed person to use when writing the Tibetan dbu-chan script.
To produce the proper thickness of horizontal strokes, the width of the pen nib should be about 1/12th the height of the letter ka.
The pen is held between the thumb and index fingers so that, as you write, the pen may be rotated to obtain the proper tansition between thick and thin strokes. The other fingers are drawn up into a fist, though some people extend the little finger to form a surface for the hand to rest on and provide greater stability. Horizontal strokes are written from left to right and vertical strokes from the top down.
The top ("head") strokes of Tibetan letters should align with each other. This top or head (mgo) stroke is always drawn first. It should either resemble a rope that has been cut diagonally at each end as in the examples below or be diagonal at one end and bow-shaped at the other.
Other strokes are executed proceeding from top to bottom and left to right.
Shoulder (dpung) strokes should descend at an angle, curving from left to right, starting thin and increasing in thickness.
Abdominal (sbo) cross strokes should resemble the blade of a curved knife or a crescent moon, thick in the
middle and thin at both ends.
In complex "stacks" all elements of the stack are usually adjusted in size and shape. The shape and angle of subscribed zhabs kyu (vowel sign "u") differs dependent on the letter or combination it occurs with.
There are several styles of dbu-can script which vary slightly - the design of the examples I've made for this page are based on one style used for writing religious texts. For combined letters only a few illustrative examples are given.
(See "Elements of the Tibetan Writing System" - for tables of all standard letter combinations.)