Very necessary when ripping sheets of plywood.  Directions are poor.  This attachment should be put on before table saw is set up as it says saw should be placed upside down to install.  My saw was already mounted on a rolling stand.  I got it done without taking the saw off the stand but it was a pain in the butt.  This support could have used a little more design time, it works but it is not great when compared to other brands.