66 GREENHOUSE CONSTRUCTION AND HEATING. 
invariably hung either directly to the ridge-plank, or else 
to a “hanging piece” fixed to it (see Fig. 31), by means 
of hinges of some kind. The ordinary ‘‘ butt’ hinges are 
however very unsuitable, as, if unused for a time, they soon 
rust together and stick, with exposure to the weather, 
and when the ventilators are opened again, become 
wrenched off. What are termed ‘‘water joints” are 
better, but not sufficiently exact for anything but very rough 
work. What are termed cross-garnets are more suitable, 
but even these ‘‘stick” sometimes, and they are decidedly 
inferior to Paine’s patent joints, or hinges. These are 
made in pairs, right and left, in 
malleable cast-iron, and while 
working very truly they cannot 
possibly hang or stick ; they also 
aid in keeping the framework of 
the ventilator together (see Fig. 
53), and, lastly, they are very 
inexpensive. Piper’s patent hinge is a still stronger and 
better-finished article, very suitable for first-rate work, 
but naturally more costly than the last. 
A point gained by dispensing with hanging-pieces, and 
hanging the ventilators directly on to the ridge (in this case 
their upper edges must, of course, be bevelled, or champ- 
fered, to the proper angle), is that the joint. is brought 
under the capping (where this is used), and any ‘‘drip” at 
this point thus prevented. A hanging-piece is, however, 
more easily fitted closely to the ridge, and if its lower edge, 
as well as that of the ventilator, is planed quite true, the 
joint will be so close as to be almost, if not quite, watertight. 
Care must, however, be taken in all cases not to hang 
FIG. 53. 
