34 VEGETABLE FORCING 
Glazing.—Greenhouse glass is usually lapped when 
laid, although it is sometimes butted. The glazing 1s 
performed more rapidly when the glass is lapped, and it 
is much easier to replace broken panes. There is also less 
leakage when the panes are lapped. The chief objection 
to lapping is that more or less dirt and soot collect be- 
tween the laps. Butted glass must be set with very great 
care in order to make the joints water-tight. A variety 
of glazing points is on the market. 
Previous to glazing, all wood parts of the greenhouse 
should be primed with one coat of paint. The sash bars 
Fig. 21.—Bench with pipe frame support. 
should be perfectly dry before putty is applied, and the 
putty should be of the best grade and kept soft by the use 
of linseed oil. It may be applied with a putty bulb, 
machine or knife. It is most convenient to begin at the 
end of the house and the eaves, and then to work up 
towards the ridge until the first row is completed, next 
laying the second row, and so on until the roof is finished. 
Sometimes the putty is applied on the outside of the 
