Ive tried to get the bit I need to show in this picture, but failed I think

I'll try my best to explain.
So, where 2 sliding doors meet theres always an overlap, whihc seems inaccesible, and I cant seem to get this area clean, are there any tricks that can be used to be able to achieve this?
The strip Im talking about is about 1 1/2 inches wide and the full height of these doors, which is about 12', and just too thin to get fingers and a cloth in between.
Thanks.
Matt