Skeletal drawings:

A further simplification is frequently employed in which only the carbon-carbon bonds are displayed. This is a skeletal drawing of the molecule. Together with such types of drawings, it is understood that a carbon atom is exist at each bond junction and that every carbon has enough hydrogens attached to make up four bonds.

Figure:  Skeletal drawing of cyclohexane.

Straight chain alkanes can also be presented through drawing the C-C bonds in a zigzag fashion.

Figure: Skeletal drawing of butane.