In parallel bar dips is it the backs of the arms parallel to the floor or is it well below that? (whatreallybuildsmuscle.com)
If you don't have a bench or a straight bar to perform dips, you can instead use a chair for the bench dips or two chairs for the straight bar dips. (ashotofadrenaline.net)
A lot harder and a bit different version of the dip is the parallel bar dip which builds strength and mass. (fitnessandpower.com)