The line out in sevens normally consists of 3 forwards from each team and a scrum half. One player throws the ball into the line, one player jumps for the ball and the other two players support the jumper. The player jumping for the ball should hopefully catch the ball and pass it back to the player that threw it in as they run round to pass to the backs.
There aren’t many line outs in sevens as the game is more about possession then territory but you can expect to have a couple during a game. As a result you probably won’t have a specialist player to throw the ball in. It’s best to play to your strengths, remember that the player throwing in will probably have to pass a long pass to the backs, so you might find it better for your scrum half to play this role. The important thing is they throw the ball in straight and can get it away quickly. If they threw it in underarm it doesn’t matter as long as you get the ball back.
The next most important player is the jumper. They should be a good ball winner in the air and a size which means the other forwards can support the player safely.
To set the line the two forwards should stand parallel to
the player throwing in as shown below. You want to make it difficult for the
opposition to predict where the ball will be thrown in, so I’d advise the
jumper starts a meter or two behind the front of the line out and moves to the front before jumping. The new rules mean the jumper must start in the line and can't enter. The jumper should 'jump down' ( a low jump to squat) the jump high keeping their legs straight to help the lifters. The supporting players should stand with both feet and
hips square in the direction of the player to be lifted.
Wait till the jumper is reaching the top of their jump and is ready for the pass. The player throwing the ball (hooker) should then run round to catch a pass and then pass the ball out to the backs.
One of the forwards should then follow the line of the ball to run the hard line. If the ball gets to the end of the line the forward is then an option for a short pass inside to hit through the oppositions defense or hit a whole.