Sometimes you just cannot reach, or it is hidden under machinery and simply unaccessible.
Blind Rivets are multi-piece rivet assemblies, capable of being installed from one side of the workpiece. Traditionally, blind rivets were used on aircraft leading edges, trailing edges, and close out areas which are limited to access to one side of the structure. Current blind rivet usage has expanded to many additional areas of the aircraft in an effort to decrease labor expense and to address the ergonomic issues of solid riveting.
This is the beauty of Blind Rivet POP® technology. "Blind Setting" allows for fastening from the front, and the POP® line of products has solved numerous industrial problems since it's creation.