Te-no-uchi literaly means "within the palm," and refers to a short stick-like weapon made of iron or wood. The Te-no-uchi could be as short as 10cm in length and easily hidden in the palm, or as long as 20cm and thus protrudes on both sides of the palm.
The shape and design of the Te-no-uchi vary. Some are well balanced and decorative, such as the one displayed in the attached photo, while others are functional but simple and dull. Wooden Te-no-uchi are usually an improvisation that could be produced easily by anybody. The shape of the wooden type is usually thick at the center, and thin at the tips. Such a shape is necessary to provide sturdiness.
The Te-no-uchi has a rope attached at its center, which serves to secure the hold of the weaon, but can also allow to swing the Te-no-uchi (see video demonstration). The rope is made primarily of silk, cotton, or leather.
Te-no-uchi was an effective weapon of self-defence for high-ranking samurai who could not carry swords in formal settings within a castle, but was also used by lower ranking samurai as well as shinobi who could carry it as a hidden weapon.
Te-no-uchi techniques would normally begin from a natural stance (shizen-tai) from which it is possible to strike with either tips or the main body of the weapon. It can also be used to apply pressure on weak-points (kyusho) and execute joint manipulations in order to control the opponent.
In the following video demonstration you can see the various usages of Te-no-uchi, including a defence against a sword attack.