They stay on very well,
In this photo there is a spring that is not shown but it is where the blue arrow points. When you push up on the bolt towards the bottom of the frame the two in the aluminum block are pushed up and the bumper slides out
In this photo there is a spring that is not shown but it is where the blue arrow points. When you push up on the bolt towards the bottom of the frame the two in the aluminum block are pushed up and the bumper slides
out as seen here