76 GREENHOUSES 



It is milled from a 2 x 4, or a 2 x 6-inch tim- 

 ber, the size depending on the width of the 

 house. The form varies according to the 

 method of attaching the ventilators. (See 

 Chapter VIII). 



Ventilators. These are fully discussed in 

 Chapter VIII. 



Ventilator Header. This is a member up- 

 on, which the lower side of the ventilator 

 rests. It is cut and grooved at the factory 

 so as to fit over the sash bars and to receive 

 the edge of the glass of the roof in its lower 

 side. 



Sash Hanging Rail. When side ventilat- 

 ing sash are used a special piece is sometimes 

 placed immediately under the eave plate or 

 gutter, to which the sash are hinged. This is 

 known as a sash hanging rail. Sometimes 

 the sash are hinged directly to the plate or 

 gutter. 



Weather Strip. Because of their construc- 

 tion and the method of hanging, the roof 

 ventilating sash do not fit down tightly upon 

 the sash bars but leave wedge-shaped open- 

 ings. These are closed by pieces known as 

 weather strips. 



