Scrambling Convention is used to find a fit, when opponent's bid shows a preemptive fit and we seem to have a fit as well.
The idea is, that we are using no trump bid to show 2 suits, and partner starts bidding from the cheapest suit in which fit is possible. That way we shall find all our possible fits on the level we are, no need to go any higher.
For example, we can use it on level 2:
|2NT||Any 2 suiter|
Similarly, on the 4th level:
|4NT||Any 2 suiter|
We can also bid it directly:
The 4♠-4NT overcall can show any 2 suiter bid. Nowadays most expert pairs bid it as an unbalanced T/O double, still it works like Scrambling convention, in order, that partner has to bid his cheapest playing possibility.
If partner has 3+♣, he bids 5♣, and when we have 5+♣, we have a fit, when we have ♦ + ♥, we bid 5♦, and partner, knowing both our suits, passes or corrects to 5♥.
When partner has only ♦ and ♥ possibilities, he bids 5♦, and we either pass it, having ♦, or we bid 5♥ with ♣ + ♥.