The rear bumper corner on the underside is always quite challenging to wrap up with vinyl wrap film, especially when there is a steep ninety-degree angle. Many wrappers might use the common way, which is pre-stretch, to handle it. But this usually leads to lifting after a while.
There is always tension at the corner when wrapping with vinyl wrap film, not to mention if it is such a severe corner. Even though you have shifted the tension away to both sides by using the common way: pre-stretch the material, and hook it behind, the tension continues to build up because of the property of the corner. And this is why the film cannot stay well for the long term.
To avoid this from happening, you have this very simple solution: First at all, apply the vinyl wrap film to the section and lock it in place. Heat up the swinging part of the material (which you will use to wrap around the two sides of the corner) a little bit to relax the film, particularly for the bottom side.
Wrap about a centimeter around the front section (the side above the ninety-degree angle), apply a little bit of heat again, and form the material, then shift the tension to the underside section with your squeegee.
By now, there should be no tension in the front section, as all the tension has been shifted to the bottom section. Most wrinkles are there at the moment. To make it flat, you should first apply a bit of heat once again to relax it.
Then, from the point of the bodyline, where it separates the two sides of the corner, make a relief cut so that your overlap can disappear to the line in the end. Once you make the cut, the tension will all be neutralized. Now you can wrap the underside first, then the front section for last.
One last move, make a flush cut about a half centimeters around the edge. By now, you will achieve a tension-free lower bumper corner with high quality and long-term durability. Happy wrapping!