You may have seen the words 'C' shape neck or 'V' shape neck well it's referring to the shape of neck. The thickness of the neck (top to bottom) and the width of the neck are both up to the guitarist. The Width of the neck is referred to as it's Radius . Certain necks have a very rounded shape which are closer to the 'D' Shape. The 'D' Shaped neck generally has more tone and sustain because it's thicker than both the 'C' and 'V' shaped necks. It is also however usually more difficult to play. The 'C' shape necks are easier to play while the 'V' shape is right between the 'D' and 'C' shapes. The tone of the neck is also influenced by what it's made of, ie. mahogany, maple. The pictures below are crosscut views where you are looking from the top of the neck. One thing about the 'V' necks found on the early Fender Strat's. The design appears to have been a mistake in the manufacturing process. The employee who normally sanded the necks was gone and some one else had sanded them incorrectly - so the legend goes.