Setup a boundary to condense the drill to six yards wide by 10 yards long. Place a tackle dummy directly in the middle of the drill. A defender should be positioned on one end of the drill opposite of the ball carrier on the other side of the drill.
Defenders learn how to track down and tackle the ball runner when there is an obstruction in between the players. The offensive player, on the other hand, learns how to utilize an obstruction to create space and get around a defender.
Start the drill with a command to the players to start running towards each other. The goal of the defender is to tackle the offensive player despite the presence of the tackle dummy in the middle of the drill. The goal of the ball carrier is to get around the defender and score a touchdown.
The narrow boundaries and the tackle dummy add an element to this drill that gives it a different situation than purely an open field tackling drill. Either player is allowed to knock down the tackle dummy if they feel the need to.
The offensive player can use his creativity to get around the defender any way he sees fit as long as he stays within the sideline boundaries. Keeping the boundaries narrow ensures that players have to deal with the presence of the tackle dummy and the runner can not simply try to outrun the defender to the side.