1-Frame-172-Gusset, Front Stand, RH  

There is a gusset fitted at the bottom side of each of the two Side Rails, 101-Side Rail, RH and 102-Side Rail, LH.
The front stand is hinged at the upper holes and the muffler’s stud is fastened at the bottom holes.
The two flanges are pointing outward and the right angle between the flange and the vertical part are pointing backward.

172-Gusset, RH and 173-Gusset, LH are each other’s mirror image. 

I am not sure what the difference is between 172-Gusset, RH and 173-Gusset, LH on the one hand and 112-Support, Silencer, on the other hand.