The scratch trade is where you lay and back the selection at the same price.
There is a tendency amongst new traders to see the scratch trade as a waste of time. Once someone has made a scratch trade, only to then see the price move the right way they tend to stop doing them. The new trader can't get it out of his mind that the scratch trade just cost him a profit and stops doing them.
However, human nature, some more than others, will always make us dwell on what we just missed out on without appreciating what we've got. A scratch trade that gets you out of the market before the price suddenly turns against you is soon forgotten about as the trader quietly congratulates his trading skills and quickly forgets all about it.
A missed profit has a different effect on many people than a saved loss of the same size has. The fewer scratch trades you do the more losses you will have, that is a fact, so therefore you need more profits just to get back the extra that you're losing. It's far better to not lose and then to not win than it is to lose and then win.