In other words, imagine that C1- C2 bond is in plane of the paper and look across the C1- C2 bond, the groups which are coming out of the plane of paper form the tails of “Y” while the groups below the plane of the paper form the heads of “Y”.
In order to convert a molecule from Fischer projection to sawhorse projection, the molecule has to be first depicted in eclipsed form. Then the steps outlined above are to be carried out in a reverse manner (Figure 3).
Figure 3
In other words, again look along the C1-C2 bond as being the plane of paper, then the groups lying above the paper form the vertical line while the groups below the paper form the horizontal bonds in Fischer projection.
To convert a Sawhorse projection to Newmann projection look along the C1-C2 bond through C1 such that C2 is not visible. Now the groups on C1 are same for both sawhorse and Newmann projection. The C2 carbon is replaced by a circle and the bonds emanating from C2 being retained in their actual spatial location (Figure 3).
Figure 3