106 VEGETABLE GARDENING 
156. The frame. — The frame may be made of wood, 
concrete, brick or stone. The most common material is 
wood, although concrete is more durable. Of the woods, 
locust, cedar and chestnut make the most durable frames. 
A common plan is to use either locust or cedar for the 
posts, and chestnut or other less durable woods for the 
sides and crossbars. The frame may be of any desired 
length, and wide enough to accommodate the sash. That 
is, the width of the frame at the top should be about Y 2 
inch less than the length of the sash. 
The upper or north side of the frame should be 6 inches 
higher than the lcwer or south side, in order to give the 
proper slope. This can be easily accomplished by using 
boards of 6 and 12-inch widths. Usually one 6-inch and 
two 12-inch boards or planks are sufficient for the upper 
side of the pit, and two 12-inch pieces for the lower side' 
the boards should always extend to the bottom of the 
pit. The posts should be made of 2x4-inch lumber, or 
heavier. It is usually necessary to remove some soil at 
the sides of the pit where the posts are to be placed. The 
best frame will be made if the boards are not more than 
12 feet long, and posts driven at the ends and midway 
between. 
Crossbars or slides are not always provided, but they 
possess so many advantages that frames should seldom 
be made without them. A 2x3~inch piece is about the 
right size, and should be sound and surfaced on the upper 
side. Some gardeners prefer a ^-inch strip in the middle 
of each crosspiece to prevent binding of the sash — a pro- 
vision that is well worth while making. The sash can 
then be handled with much less annoyance. 
When placing the crossbars, great care should be ex- 
ercised, for if they are too close together the sash will 
bind and greatly annoy the attendant. If the sash are 
3 feet wide, the distance from center to center of the 
crossbars should be at least Y 2 inch more than 3 feet. 
