The methods of door construction thus far described are not protected by patents, and can be adopted by any one having the necessary facilities. There are, however, a few devices for doors that have been patented, and can therefore be used only by the patentees or under license.
Fig. 233 shows a section of stile (half full size) of a patent veneered door* the patent applying to the manner in which the veneer is applied. The interlocking of the core and veneer doubles the gluing surface, thus preventing the veneer from peeling, warping or checking. This construction is especially desirable for outside veneered
* Made by the Compound Door Company.
There are also special kinds of doors, such as flexible doors, or rolling partitions, revolving doors, etc. These are described in Appendix A. Special methods of hanging doors of several folds for closing wide openings are described in Section 213. .