300 THE HOUSE FLY—DISEASE CARRIER 
top near the ends, to prevent warping; it is hinged in 
back to a strip i inch thick, 3 inches wide, and 20 
inches long, which is fastened to the seat. Cleats 
may also be nailed on the seat at the sides of the cover. 
On the inside of the backboard, 12 inches above the 
seat, there should be nailed a block (1), 2 inches wide, 
6 inches long, extending forward 3*4 inches; this is 
intended to prevent the cover from falling backward 
and to make it to fall down over the hole when the 
occupant rises. 
On the floor of the box (underneath the seat) two 
or three cleats are nailed in such a position that 
they will always center the tub; the position of these 
cleats depends upon the size of the tub. 
Back door .—In making the back of the privy the 
two center boards were sawed at the height of the 
bottom of the seat. The small portions (c 2 ) sawed 
off (23 inches long) are cleated (0) together so 
as to form a back door which is hinged above; a 
bolt or a button is sufficient arrangement to keep the 
door closed. 
Front door .—The front door, Fig. 38, is made by 
cleating ( p ) together three boards (Q) 1 inch thick, 
10 inches wide, and (when finished) 6 feet 7 inches 
long; it is best to use three cross-cleats ( p ) (1 inch 
thick, 6 inches wide, 30 inches long), placed on the 
inside. The door is hung with two hinges (6-inch 
“strap” hinges will do), which are placed on the right 
as one faces the privy, so that the door opens from 
the left. The door should close with a coil spring (cost 
