One interesting thing that you can do with domino topples is to set them up on different levels, such as on a coffee table and on the floor. A domino at the end of a line falls off the table and strikes a strategically placed line of dominoes on the floor to continue the topple. Placement becomes critical, and there are some techniques that you can employ to make it foolproof. We decided to make a device that did the same thing. The image on the right is mostly self explanatory, but note that there is a stop that keeps the arm in a horizontal position. The vertical dowel is cut so that it overlaps with the top of the domino by about 1/2" (13mm). The other dowels are simply a means of creating a lightweight plunger so that the size of the target for the falling domino is increased making it virtually impossible to have a break in the topple. The arm has a through hole that is slightly larger than the cross dowel. We also included a pair of nylon washers between the arm and the vertical supports to ensure that the arm rotated freely.