I reembled my Mossberg 500 410ga. and i have leftover pieces.?

I recently received a Mossberg 500 410ga. from a friend. When i got this shotgun it was in need of a thourough cleaning so like i have done countless times with my other firearms i set it on my table and got my cleaning kit, and tools out. It was not completely foreign to me this being my first mossberg shotgun but it definitely wasn't as simple as my Rem. 870. After removing the barrel, forearm, firing pin, lift, and other parts i noticed a couple pieces that had fallen out after i removed a screw. I had never seen pieces like these but i didn't worry about them very much. After i had cleaned each part of the gun i began to reemble it, I didn't realize until the gun was reembled that the two pieces which fell out were still on the table. I have no idea what these are for but i do know where they go. They came from inside the shell ejection port and were held in by a screw. what i don't know however is how they are supposed to fit in there. One is smaller than the other and i don't know which one goes on top and which goes on the bottom. Any help would be greatly appreciated. Thank you.