This section is from the book "Complete Self-Instructing Library Of Practical Photography", by J. B. Schriever. Also available from Amazon: Complete Self-Instructing Library Of Practical Photography.
Trimming Prints. If prints are to be mounted, trim while wet, in the following manner: Take a square sheet of glass, wet it and place the print - face down - on the same. Turn the glass over and the prints will then be on the under side - face up. Move the print to the edge of the glass, and with a pair of sharp shears trim one end of the print; then slide the print to the other edge of the glass, and square it to the trimmed edge of the print, and trim in a like manner. After the print is trimmed, place it back in the tray of water and proceed in like manner with the rest of the prints until all are trimmed; then lay them out on a glass plate or other smooth surface, face side down, one print overlapping the other until all are on the plate. If you desire to trim prints when they are dry, a trimming board may be used.
Mounting Prints. Remove the excess water, by pressing the prints with the palm of the hand, and then with a dry blotter. With a paste brush apply ordinary starch or prepared paste to the back of the top print. (See Illustration No. 57, applying paste.) Pick the print up at one corner (See Illustration No. 58), bringing the paste side in contact with the mount (See Illustration No. 59). After carefully squaring the print on the mount, place a clean, dry blotter over it and rub down with the ball of the hand, or with a squeegee roller, removing all air bubbles and securing perfect contact with the mount. Allow it then to dry. Any superfluous paste on the print or mount should be removed with a soft wet sponge. For further instruction on Trimming and Mounting, see Chapter XXV (Velox Printing And Developing. Introduction).