Preparation - you need a piece of string or rope at least 1 yard long, and a pair of scissors.
Show the children the rope and tell them that it represents communication - how we talk to others.
Our sins - the bad things we do.
State that you are now going to demonstrate this problem by cutting the rope (Prayer line).
Hold the top of the rope in one hand, and hold the middle of it with the other.
Bring the middle part of the rope to the top, but as your bottom hand reaches your top, swap the middle for a piece of rope about 5 inches from the top.
This will take place behind your top hand, so will not be noticed. With a little practice you will soon get pretty good with this. It will appear to your group that you are now showing the top and the middle of the rope in your top hand, but what you are really showing is the top and a section of a few inches below the top.
Cut the rope where it is looped. You have actually cut off just a small top portion, but have appeared to cut it in equal halves.
While still concealing the top of the rope behind your hand, tie the small section of rope around the middle, and release for all to see.
Say that the knot around the centre stands for sin, and prevents your prayers reaching God. Explain that some people try to deal with the problem themselves by reducing their sin. Cut the ends off the knot to make it smaller. Obviously this doesn't work, because the problem (knot) is still there. Explain that some people try to hide their sin. Cover the knot with your hand. This doesn't work either, because we cannot hide anything from God.
Explain that the only way to remove sin is to bring it to God, tell Him you are sorry for it, and ask Him to forgive you. Say, "Imagine my right hand is God, and I am going to bring this sin (knot) to Him." Hold one end of the rope in your right hand, and begin to wrap the rest of the rope around it with your left hand. As you reach the knot - and while still continuing the wrapping - slide off the knot, and keep concealed in your left hand. Unwrap the rope, showing that it has been completely restored! No one will notice that it is now slightly shorter than when you started..