Blind rivets for joining steel and aluminium sheet components, set from one side where there is no access to the back of the joint.
Aluminium body with a carbon steel or stainless mandrel, and a carbon steel version. The combination matters: pairing aluminium sheeting with the wrong mandrel material sets up galvanic corrosion at the joint.
Heads can be powder coated to the colour of the sheeting — UV-resistant polyester, 50–60 µm.