I am confused about the explanation given for the the rule in inhiraaf. It said in the rules section...

Question
Jazakumu'Allahukhayrun for this website. I am finding it very beneficial.  I do have a question on the characteristic of letter ra.

I am confused about the explanation given for the the rule in inhiraaf.  It said in the rules section, "The   raw' sticks at the left and right of the very tip to the second part of the articulation point ie. the gums of the two front teeth"

My question is how is the second articulation point for raw at the gums of the two front teeth?

Wasalam
Answer
Wa alaikum assalaam wa rahmatullahi wa barakatuh,
May Allah grant us purity of intention always and increase us all in beneficial knowledge.
Each articulation point which has a specific location has two parts to the articulation.  Sound is produced by the collision of two bodies or separation of two bodies for most (but not all) letters.  In the case of the , the two parts which need to collide or separate are 1) the tip and top of the tip of the tongue and 2) the gums of the two top front teeth.  We cannot produce the sound of the without both of the these parts hitting  each other or separating from each other. 

Wa assalaam alaikum wa rahmatullah