You're in a shoe shop, second in the line for the sales register. Behind the shop assistant on the display is a pair of shoes which you have seen and which you absolutely must have. 

The female shopper in front of you has seen them also and is eyeing them with desire. 

Both of you have forgotten your purses. 

It would be totally rude to push in front of the first woman if you had no money to pay for the shoes. 

The shop assistant remains at the register, waiting. 

Your friend is trying on another pair of shoes at the back of the shop and sees your dilemma. She prepares to throw her purse to you. 

If she does so, you can catch the purse, then walk round the other shopper and buy the shoes. 

In a pinch, she could throw the purse ahead of the other shopper and, while it is in flight you could slip around the other shopper, catch the purse and buy the shoes. 

Always remember that until the purse has actually been thrown, it would be just plain wrong to be forward of the other shopper.