52 DEPARTMENT BULLETIN 1216, U. S. DEPT. OF AGRICULTURE 
the tile during the test. A strip of cloth may, if desired, be attached to the 
inside of the upper frame on each side, along the lower edge, to prevent the 
escape of sand between the frame and the tile. 
v ^r 
m 
r m 
x 
y 
m 
T ' P|| 
v-J 
/ 
\\i* 
I 
\ 
- > 
!•• '■■; '. \ ' 
1 
Wmim 
19. When two-edge bearings (fig. 20) are used, the ends of each specimen 
of tile shall be accurately marked in halves of the circumference prior to the 
test. 
The tile to be tested shall be supported by a metallic knife bearing 1 inch 
wide and extending the length of the tile. Before the tile is placed, a fillet of 
plaster of Paris and sand 1 inch wide, and thick enough to compensate for all 
the inequalities of the tile barrel, shall be cast on the surface of the knife-edge 
