THE IOWA SILO 77 



on each side of the opening. These jambs are 

 made of reinforced concrete and may be used with 

 either clay or cement blocks. The horizontal reinforce- 

 ments of the wall hook into the vertical reinforcements of the 

 jamb. The jambs are tied together at intervals of 4 or 5 feet 

 by steel within the crosstie block. This steel not only extends 

 into the vertical jamb, but, in order to be more secure, 

 extends several feet into the wall on either side of the jamb. 

 As shown in Fig. 19, these crossties may be of steel and pro- 

 tected from rust by being incased within the clay blocks 

 filled with concrete or within the concrete alone. When the 

 wall has been completed to the height at which it is desired to 

 commence the door, two blocks are laid upon the wall across 

 the doorway. These should be placed out far enough so that 

 the door may be set down inside without touching the 

 cross blocks. The shoulder or ledge thus formed should be 

 1% inches wide. Through this crosstie, and extending into 

 the hollow spaces in the blocks on either side of the door- 

 way, should extend the reinforcing steel, unless cement 

 blocks are used, in which case this is not practicable, and the 

 reinforcing steel may simply be hooked into vertical steel. 

 Upon this bottom crosstie must be placed the outer half of 

 the continuous door form. Then the vertical reinforcement 

 may be hooked to the lower crosstie and secured in a vertical 

 position by tieing it to the form. Then the horizontal rein- 

 forcement of the wall may be hooked to or placed inside of 

 the vertical reinforcement. When the wall is completed to 

 the top of this form, the inner portion of the form may be 

 bolted to the outer. The form, crosstie, and the wall into 

 which the steel projects should be then filled with moderately 

 wet concrete made up of reasonably fine gravel. The second 

 form may be secured to the first by means of 2x6's. The use 

 of the second form is similar to the first. It will thus be seen 



