nylon-wrapped metal strings, some argue that nylon-wrapped metal strings cannot replace silk strings for their refinement of tone. Further, it is the case that nylon-wrapped metal strings can cause damage to the wood of old qins. Many traditionalists feel that the sound of the fingers of the left hand sliding on the strings to be a distinctive feature of qin music. The modern nylon-wrapped metal strings were very smooth in the past, but are now slightly modified in order to capture these sliding sounds. Although silk strings tend to break more often than metal nylon ones, they are stronger than one may be led to think. Silk is very flexible, and can be strung to high tensions and tuned up to the standard pitch that was proposed by mainland China (5th string at A) without breaking. Also, although they may be more likely to break at higher tension, they are hardly discardable once a string has broken. Silk strings tend to be very long (more than 2 metres) and break at the point where it rubs on the bridge. One simply ties another butterfly knot at the broken end, cut the frayed bit, then re-string. In this way, the string can be re-used up to ten times for the thinner strings (three or four times for thicker ones), and every set includes an extra seventh (most likely to break) and probably a fourth (next most likely to break). Because silk strings break easily, there are very few that survive from the past dynasties. Stringing the instrument Traditionally, the strings were wrapped around the goose feet 『雁足』, but there has been a device that has been invented, which is a block of wood attached to the goose feet, with pins similar to those used to tune the guzheng protruding out at the sides, so one can string and tune the qin using a tuning wrench. This is good for those who lack the physical strength to pull and add tension to the strings when wrapping the ends to the goose feet. However, the tuning device looks rather unsightly and thus many qin players prefer the traditional manner of tuning; many also feel that the strings should be firmly wrapped to the goose feet in order that the sound may be "grounded" into the qin. Further, one cannot wrap silk strings around such tuning pins as they tend to break more easily