back flush a Material from one location to another location

Hi all Experts

My client want to back flush material (A) from one location (L1) to another Location (L2) using T.code MB1B and from L2 he issue it for production.

My question is Does he wants to Extend material (A) in both the Location (L1 & L2)? I think no need to extend.

Pls confirm...

Regards

K.R.Srinivasan