If you want your shelves to stay up you need these!
The 10" position shelf brackets are for use with the following:
9" (22.86cm) deep Linen shelving
10" (25.4cm) deep Shelf & Rod shelving
16" (40.6cm) deep Shelf & Rod shelving, with hang bar 10" (25.4cm) from back wall.
The shelf support brackets are needed to support the shelf and therefore you would need one every 36" (91.4cm) along the shelf's length, and also one at each end if you are creating 'open ends' or floating shelves, where 1009 - shelf support poles, or 974/980 - wall brackets have not been used.