For any coach, the 'junk' defense is employed for one of two reasons.
First, your opponent is looking to catch you off guard and use the element of surprise to interfere with your offensive rhythm.
Secondly, an opponent might feel the bulk of offensive production might come from one (maybe two) players and regards the rest of the team as non-threats.
Four years ago we had a player in our league out of Central Oregon that was leading the scoring average by a mile-scoring 32 points per game-we elected to implement a box and 1 defense to throw off our opponents rhythm as well as kennel the explosion of offensive fire power this player possessed.
Junk defenses come in two very distinct combinations.
The box and 1 (sometimes referred to as the diamond and 1) and the triangle and 2.
Teams often attack the junk defense using their regular offensive sets to force open opportunities for their scoring threats.
This type of philosophy is what I refer to as the traditionalists.
Tradition says, if you run your offense with precision no one will be able to beat you.
These are also the coaches who can be found saying, "defense wins ball games".
There is absolutely nothing wrong with this approach.
Yet, there are those who are opportunists like myself who rely on certain zone busting principles such as: Attacking the Interior Ball Movement Spacing Faking a pass to make a pass to counter the junk.
Offensive maneuvers like back screens, high/low situations, and on-ball screens are the most effective means of scoring points on an junk defense.
Finally, it is important to practice and implement specific offensive sets your team will use against a box and 1 or triangle and 2 alignment.