The signature red binder.
Binders are a sort of folder with a hard covering that can have a variety of different contents stored within them. In the game, the binders are simply blocks located throughout the facility and cannot actually be used, however are usually located next to a handful of documents, one of which may be able to be actually picked up and read. They are either red or grey. There's also an object in the game that looks like a binder with a dark red covering, but could also possibly be a book as well.
Gallery[]
The signature red binder.
The signature grey binder.
The signature red binder and signature grey binder, next to each other. There is one (1) red binder on the far left, and three (3) grey binders stacked next to it. Most notably, the third grey binder, which is also the rightmost grey binder, is leaning on the second to the last grey binder.