A sawhorse projection is a view of a molecule down a particular carbon-carbon bond. Groups connected to both the front and back carbons are drawn using sticks at 120° angles.
It is similar to a Newman projection, but it shows the carbon-carbon bond that is hidden in a Newman projection.
Just as with Newman projections, you can draw sawhorse projections in eclipsed and staggered conformations.
Below are two sawhorse projections of ethane.
They are called sawhorse projections because the eclipsed conformation looks like a carpenter's sawhorse.
Sawhorse projections are useful for determining if two molecules are enantiomers or diastereomers.
They make it easier to see if the structures are mirror images or superimposable.