Guidonian hand
In Medieval music, the Guidonian hand was a mnemonic device used to assist singers in learning to sight-sing. Some form of the device may have been used by Guido of Arezzo, a medieval music theorist who wrote a number of treatises, including one instructing singers in sightreading. The hand occurs in some manuscripts before Guido's time as a tool to find the semitone; it does not have the depicted form until the 12th century. Sigebertus Gemblacensis in 1105–10 did describe Guido using the joints of the hand to aid in teaching his hexachord. The Guidonian hand is closely linked with Guido's new ideas about how to learn music, including the use of hexachords, and the first known Western use of solfege.
Pugio
Like other items of legionary equipment, the dagger underwent some changes during the 1st century AD. At some time in the first half of the 1st century AD a rod tang was introduced, and the hilt was no longer riveted through the tang and was instead secured only at the shoulders of the blade. This in itself caused no great change to the pugio's appearance, although the archaeological evidence strongly suggests that the rod tang was less secure and that handles attached in this way could become detached, a possibility that may be proved by the existence of two surviving pugios from different sites which both retain replacement handles, one of which is a recycled sword grip. Some of the blades associated with rod tangs were narrower (under 4.5 cm (1.75 in) wide), with little or no waisting, or reduced or virtually non-existent midribs (type 'C' blades).