The base line, the line in the back.
the area that you serve into is the same as in singles. The server may stand anywhere in between the center mark and the doubles sideline
Yes, as long as it touches a line (even the outside of the center line) it is considered in. -Te lol
No, you CANT step over the serving line when you serve in volleyball. The "ref" on the side of the court, on the stand, will call it, and give a point to the opposing team. Usually the line judge should call it....
It's where you stand when you serve. Behind the baseline in one of the four corners of the court. Best way I can say it.
No. The interior lines (half-lines) on tennis courts determine the service court, into which the serve must be made. An ACE is any legal serve that is not successfully returned by the opponent, winning the point for the server.
They Can Serve behind the baseline BEHIND and in line with the alley if that's what you mean. http://www.tennistips.org/doubles-tennis.HTML
If the serve touches any part of the service box (including the white lines that enclose it), then the serve is in. This includes barely nicking any part of the line.
Almost all of your joints are used in tennis, but the main ones in a tennis serve are the knee joints, and elbow joints.
Behind the out-of-bounds line. how far back from the line depends on what type of serve you are doing, if you are doing a jump serve you'll probably stand back a ways, if you are doing an overhand serve it depends on how strong of a server you are or how experience you are.
International Tennis Federation.
You can hit an underhand serve in tennis; however, the overhand serve is more effective because it is more powerful. That is why you don't see the underhand serve used much.