THE WOODWORK. 59 
coat of tar, an excellent gutter may be obtained with a very 
slight extra expenditure of material and labour; but in a 
level house, if such a gutter is of any considerable length the 
drip must be sloped to secure a fall, and in this case it should 
be cut from a wider board. 
Double plates, or gutters, of cast iron are now manu- 
factured. These, bolted on to iron uprights, or posts, are 
at once very strong and inexpensive, and will be found most 
useful where several span-roofed structures are erected side 
by side (see p. 14). 
The Ridge.—This is a stout plank employed to butt the 
upper ends of the rafters or sashbars against, in order to 
‘separate and keep them at their proper distance. A good 
average size for a ridge-plank is Zin. by 14in. or 1Jin.; in quite 
small structures a somewhat slighter piece may be employed, 
and for houses of 20ft. or more in width a heavier ridge, 
of say Sin. or Yin. by 1ldin. or lin. stuff is better. A 
square groove, about 3in. wide and din. deep should be run 
along both sides to take the upper edges of the glass (see 
Fig. 45) ; but where the roof is composed of framed lights; 
or sashes, no groove is necessary. In the ridge-plank for 
a lean-to structure, a groove should be run on one side 
only. This (plank) is usually secured to the wall by means 
of stout nails, driven into wooden plugs in the brickwork, 
or with holdfasts. The groove should be run about halfway 
up the plank, or rather less, as shown, but, in any 
case, there must be width enough abore the bars (rafters) 
to permit of the ventilators being properly hung. If the 
ventilators are 2in. thick, there should be a clear 2jin, 
of ridge above the top of the rafters, and if the pitch 
is at all steep, 3in. will be better. The groove, which 
