If the roof is already constructed, horizontal lines should be drawn between the hip rolls at equal distances (say 6 in.) apart, measured on the surface of the roof as shown in the elevation half of Fig. 1. The lower half of the figure, and the vertical dotted lines, are drawn only as aids to finding the true position in the elevation of the hip rolls to the centre bay, so as to be able to measure the width of the latter at all parts. Similar horizontal, and a centre perpendicular, lines are to be drawn on the piece of lead to be used, and tie dimensions transferred one at a time from the roof to the lead, and the points joined together by freehand, as shown by Fig. 2. Outside the lines thus found, draw others 4 in. and 8in. distant for the under-cloak and over-cloak respectively. The sides of the bay are then bossed upright ; or, if the contour of the roof is very round or very hollow, they can he doubled down flat until placed in position, and afterwards worked up and dressed to the rolls. If the bays are not very large, the nailing on the top end, and also the under-cloaks to the rolls, will support them. With a roof of this shape the grip of the metal on the rolls will also help to support it. If the bays are put on in two pieces, or if laced rolls are used between the hip rolls, further support is obtained without the use of soldered dots. About three copper tacks can be used for each bay to hold up the bottom edge. The covering for the top should be bossed out of a round piece of lead, and the bottom edge should lie on the roof about 6 in. to 0 in., to cover the nailing and make it watertight at that point. Copper nails should be used in preference to iron nails.

Fig. I.

Fig. 2. Setting out Lead Bays for an Ogee Roof over a Ventilator Octagonal on Plan.