"55" is a full court match up man to man press. The following points are important in the "55."
1. No Fouls-show the official your hands-fouling negates hustle.
2. All defenders must see the ball.
3. Be in an intercept position, ready to shoot the gap.
4. Deflections-steal off the ball, trap on the ball
5. Make the offense dribble
6. Trap the dribble when your teammate is on the dribbler's side, not when trailing (see diagram).
7. Sprint out of traps.
8. Switch on all screens.

Here x1 and x2 are in a three quarter denial position where they can see the ball, and their hands are out.
x4 is very active on the ball.
x1 wants the ball to be in-bounded below the foul line extended. If so, x4 traps immediately. x2 would rotate up and to the middle of the floor.

If 1 receives the ball foul line extended then x4 must get back ahead of the ball to the middle of the court.
x1 will get right up on 1 to force him to dribble. If x1 gets beat up the sideline then x3 will come up to trap, only if x1 is on the side of 1, not trailing. If x1 is trailing, then x3 will "stunt" or fake at 1 but not commit until x1 recovers to the side of 1. Everyone rotates on the trap.

If x1 gets beat to the middle of the floor, then x4 will trap the ball.

On a ball reversal in the backcourt x4 will go back on to his man and force 4 to dribble. If he dribbles at 2 then x2 will come up and trap. x1 rotates up and to the middle of the court to take away 3's flash. x3 protects deep, and x5 looks to steal a pass to 2 if possible.
x5 may have to "stunt" at 2 until x2 recovers.