French WW2 M36 (?) Backpack question

[Nezvanov]

Hello everyone. Brand new here and hoping someone can help me with some info. Just picked up a very nice but well-worn french WW2 backpack. I believe it is an M36, standard issue, one cargo compartment, two side pouches and large covering flap with what appear to be m1915 brown leather arm straps. My question concerns a large inner flap sewn into the lining of the 'outer' flap. What was it for/how was it used? I cannot see how it could contain anything or really protect anything. Does anyone have an idea how it was intended to be used? Sure appreciate any insights. Thanks, Nezvanov

[Wagriff]

Any photos possible? I'm having abit of a time picturing. If it is what I'm thinking,it should be simple.

[Ubique]

Back packs today often have a zippered pocket in the top flap, usually for maps. Possibility?

Oz.

[lebus12]

Les effets portés dans le paquetage

[lebus12]

[Nezvanov]

Pics of the flap from the out and inside

[Nezvanov]

The flap is 'envelope' shallow so it appears not to be able to hold much of anything at all. Also the method of fastening it shut (upside down) as the outer flap closes and buckles is beyond me. Merci Lebus12 ...d'acour..
Je ne vois toujours pas comment tous les draps de l'image correspondent correctement!
Thank you all for your help. I thibnk I will study the images Lebus12 has sent and experiment untilo my pack is set right. Any further info is certainly appreciated. Also thanks for welcoming me with so much info.