The sidelines are the lines that run the length of the field, stretching from the back of one endzone to the back of the other endzone. Its interior edge is considered out of bounds
football_sideline(feature_thickness = 0, field_length = 0, endzone_length = 0)
A data frame of the bounding box of the sidelines
The thickness of the boundary lines
The length of the field
The length of the endzone