THE WOODWORK. 65; 
and the number of widths in the ventilator. The top rail 
should be the same thickness as the styles—these ought to. 
be cut from 2in. stuff in all cases, though in cheap work 
that 1jin. in thickness only is frequently employed—. 
and is also rebated on the inner or lower edge, for the glass, 
though a groove is sometimes run along instead. The 
bottom rail is, however, made wider—4in. to 6in.—and 
is only the thickness of the styles /ess the depth of the 
rebate—that is, its upper surface, on which the glass. 
rests, is made flush with the rebate in the styles and. 
the top rail. The smaller bars are mortised into the: 
top rail about an inch, and the lower ends just let into. 
the bottom one for about half an inch, a ‘‘ tail” of the. 
upper portion (above the rebate) 13in. or 
Zin. long, being left and tacked down to ———— 
the face of the lower rail, as shown in (WSs 
Fig. 52. Fig. 52. 
A common form of ventilator is that of an oblong, 
or nearly twice as wide (along the rails) as deep. A 
ventilator with the styles and top rail made out of 3in, 
by 2in. stuff, and about 54in. long by 24in. or 25in. deep, 
will just take three squares of 20in. by 16in. glass, and will 
cover four l4in. bars at the same distance (16in.), or three 
spaces, nicely, with an overlap of about lin. at each end, which 
is just right. A ventilator should overhang the seat by lin. 
or ldin. at the bottom. A small groove is sometimes. 
ploughed along each side of such ventilators, about tin. 
from the edge, and on the under side. This is intended to 
prevent any drip driving in between the styles and the bars 
of the roof in stormy weather, but it is scarcely necessary. 
Roof-ventilators of the usual type (see p. 33) are almost 
F 
