station 10 the body 20 is received from the assembly line track 80 with a partially flanged first sheet material 30 requiring a hemming operation that is located primarily about the rear wheel opening a roller head 400 for hemming the first sheet material 30 is outlined in the sectional views of fig4 6 and 7 the roller head 400 is of a pull type different than those used off line in that it has no compliance when pushed a shaft extends from one end of the cylinder and supports a roller that creates biasing compliance when pulled on by pulling instead of the traditional pushing of the biasing element the present invention can achieve the feature of unlimited hemming attack angles that an off line system enjoys a feature that pinch rollers can not achieve when the wheel 410 is not in contact with the first sheet material 30 the spring 420 expands between a spring plate 430 and a t head bolt 440 urging the cylinder 450 and roller 410 toward the robotic arm 50 when the wheel 410 is hooked in contact with the first sheet material 30 and the robot 50 pulls on it the spring 420 compresses between a spring plate 430 and a t head bolt 440 thus producing the positional pressure of a selected amount to produce a quality hem a robotic arm 50.