These files are for brackets to hang air tools by their quick-connectors. The straight bracket is good for most locations. The version with the 8 degree tilt to the back is for locations where vibration might make the tools shake out of the bracket, such as when they are attached to the compressor or other equipment.
Update: Even with the 8 degree tilt, tools sometimes shake out of my brackets that are mounted on my air compressor. The "vibration resistant" version of this bracket incorporates a curve to keep tools from shaking out of the hanger slot.