Ah, the dreaded U-shaped level. Launch the ball either one click right or two clicks to the left. Wait for the ball to ricochet off the bottom of the U and then hit it again on either the right half or left half of your paddle to send it up the channel.
As with level 13, you may find yourself trapped under the row of unbreakable bricks. If so, check out these instructions.
The ball will likely escape from the U-shaped enclosure a few times while playing this level. If this happens and you see the ball descending along the wall on either side, position your paddle directly beneath the long column of unbreakable bricks on that side. Watch carefully as the ball passes beyond the bottom-most unbreakable brick. Does it scoot under the brick and head towards the center of the board? Does it ricochet off that last brick and head back towards the wall? Wait until you see where the ball is going before moving your paddle into place to intercept it. When you intercept the ball on the right side of the level, try and strike it with the right half of your paddle. The ball might ricochet off the bottom row unbreakable bricks, in which case a second strike on the right side of your paddle should send the ball back up the chute. For balls on the left side of the level, use the left half of your paddle.
The best capsule to get on this level is the Multi. If you can keep the balls in play, not only are the bricks cleared out more quickly, but the transition to a slow ball speed will happen sooner. If you get a Gun, try destroying the three unbreakable bricks in the center of the bottom row. That creates a bit more breathing room under the U, and gives you a chance to damage some bricks from the bottom up.