The Erh hu (Erhu, Er-hu) is the sole stringed chinese instrument. The small corpus is covered with snake skin, and usually it is hexagonal or octagonal - sometimes also cylindrical. The Erh hu has only two strings, which are tuned in fifths. The bow is fixed between these strings.
The Erh hu is often called the Chinese violin. But the designation knee violin would probably be more appropriate in our culture, since the musician holds the instrument upright on the knees. The strings have to be touched softly and must not be pressed down to the neck, otherwise the instrument will sound a little bit too natural, similar to breaking wood or other ugly things.