This is the difference between the right and wrong way for a marching band to turn around a corner.
On the left, we have what you're supposed to do. Every 8 counts, a new line starts moving, and it takes 20 counts to rotate around a single pivot point to get to 90 degrees. Note that the pivot point is not the person on the end, but slightly to the inside (to the left in this illustration). Two-step spacing side to side is maintained throughout the entire move.
On the right, is an example of what (for some reason that nobody will ever understand) natural human instincts will cause you to do. Everyone starts turning too soon, and crunches to the outside (right). There is no single pivot point, because everyone is reacting to the line in front of them. Eventually, the lines start turning so soon that the rotation has nearly completed before the line even reaches the intersection.
If for some reason the band needs to stop in the middle of a turn, the example on the left would look as if you paused the video. What an untrained ensemble will tend to do, however, is continue to go around the turn and try to cover down on the other lines that have finished the rotation, leaving the back of the block completely out to dry.
With a little bit of awareness of this issue and some good ol' fashioned teamwork, a band can kill this problem fairly easily. Always be looking ahead to assess what the lines in front of you are doing, and keep checking to see what the guide points in your line are doing. Work together, keep the lines straight, keep your intervals side to side, and don't turn too soon.
![](https://i.ytimg.com/vi/WStGbEYDREI/mqdefault.jpg)