This is a plastic sleeve consisting of 2 sheets of plastic folded back on the vertical side and then heat bonded on the bottom side of the seam. The size is slightly bigger than A4 and is meant to store A4 size documents. The number of sleeves count is now 3, also known as a 4-section L-sheet. The sleeve is open on the top end and the right hand side so that the top right corner of the plastic sheet can be lifted up and documents/papers can be slotted into the sleeve. That is how the L-sheet is used. In our case, we have 3 separate slots for a 4-section L-sheet.