The serviceline is the line in front of which (nearest the net) a serve must land, and be on the proper side of the court to be considered legal and in play
tennis_serviceline(singles_width = 0, feature_thickness = 0)
A data frame containing the bounding coordinates of the serviceline
The width of the singles court
The thickness of the serviceline
This line extends completely between the singles sidelines (but not extend to the doubles sidelines)