Moving Targets for a Home Shooting Galleries, are entirely out of the question for home practice, owing to the cost of the machinery and its bulky nature; however, the same results can be obtained with the device illustrated, which is not expensive or difficult to construct.  It consists of a board placed on a slant on two posts.   On this board the moving objects roll.  These are made of plaster formed in tin-can covers.  To prevent the disks from rolling off the board, strips are nailed on as shown to make a groove for them.  At both the upper and lower end, facing boards are fastened so that the marksman cannot see the disks until they start rolling.

A number of disks are set in the groove at a time by a trigger operated with a string.  The speed of the rolling disks with a string.  The speed of the rolling disks is governed by the slope.

G. P. Lehmann - Poplar Science Monthly