With regard to the size of the flange, this will depend upon the strength of the adhesive used and the stiffness of the material. Generally speaking, the larger the flange the better, for a narrow flange tends to turn up and must be held down longer than a wide one.
A good general rule to remember when joining two pieces of material is this—that it is always the thinner of the two that is to be pasted or glued. This must be borne in mind when using the second method of joining cardboard or paper edges.
Fig. 3a
Fig. 3b
(2) Using paper hinges. The hinge should extend the whole length of the edges that come together, as in Fig. 2, where pieces of cardboard A and B are joined by the hinge a b c d e f. Before pasting the hinge must be folded along b e, care being taken that b e is at right angles to a c and d f.
The sides, bottom, and roof of the Noah's Ark are joined together by paper hinges (Chapter X).
(3) Wherever it is necessary to join curved edges, the flange must be cut as in Fig. 3a, flange a b c d. Fig. 3b shows paper curved and flanges bent down ready for pasting.
This is the method used for fastening on paper funnels, the bottom of the paper mug (Fig. 57, Chapter IV), etc.