<P> The flat backs of most viols have a sharply angled break or canted bend in their surface close to where the neck meets the body . This serves to taper the back (and overall body depth) at its upper end to meet the back of the neck joint flush with its heel . Traditional construction uses animal glue, and internal joints are often reinforced with strips of either linen or vellum soaked in hot animal glue--a practice also employed in early plucked vihuela construction . The peg boxes of viols (which hold the tuning pegs) were typically decorated either with elaborate carved heads of animals or people or with the now familiar spiral scroll finial . </P> <P> The earliest vihuelas and viols, both plucked and bowed, all had sharp cuts to their waists, similar to the profile of a modern violin . This is a key and new feature--first appearing in the mid-15th century--and from then on, it was employed on many different types of string instruments . This feature is also key in seeing and understanding the connection between the plucked and bowed versions of early vihuelas . If one were to go searching for very early viols with smooth - curved figure - eight bodies, like those found on the only slightly later plucked vihuelas and the modern guitar, they would be out of luck . By the mid-16th century, however, "guitar - shaped" viols were fairly common, and a few of them survive . </P> <P> The earliest viols had flat, glued - down bridges just like their plucked counterpart vihuelas . Soon after, however, viols adopted the wider and high - arched bridge that facilitated the bowing of single strings . The earliest of viols would also have had the ends of their fretboards flat on the deck, level with or resting upon the top or sound board . Once the end of their fretboards were elevated above the top of the instrument's face, the entire top could vibrate freely . Early viols did not have sound posts, either (again reflecting their plucked vihuela siblings). This reduced damping again meant that their tops could vibrate more freely, contributing to the characteristic "humming" sound of viols; yet the absence of a sound post also resulted in a quieter and softer voice overall . </P> <P> It is commonly believed that C - holes (a type and shape of pierced sound port visible on the top face or belly of string instruments) are a definitive feature of viols, a feature used to distinguish viols from instruments in the violin family, which typically had F - shaped holes . This generality, however, renders an incomplete picture . The earliest viols had either large, open, round, sound holes (or even round pierced rosettes like those found on lutes and vihuelas), or they had some kind of C - holes . Viols sometimes had as many as four small C - holes--one placed in each corner of the bouts--but more commonly, they had two . The two C - holes might be placed in the upper bouts, centrally, or in the lower bouts . In the formative years, C - holes were most often placed facing each other or turned inwards . </P>

Two close relatives of the modern day cello were the viola de gamba and the basso di viola