In mounting sheets that are likely to be removed and replaced, for the purpose of modification, as working drawings generally are, they can be fastened very well by small copper tacks driven in along the edges at intervals of 2 in. or less. The paper can be very slightly dampened before fastening in this manner, and if the operation is carefully performed the paper will be quite as smooth and convenient to work upon as though it were pasted down; the tacks can be driven down so as to be flush with, or below the surface of, the paper, and will offer no obstruction to squares. If a drawing is to be elaborate, or to remain long upon a board, the paper should be pasted down. To do this, first prepare thick mucilage, or what is better, glue, and have it ready at hand, with some slips of absorbent paper 1 in. or so wide. Dampen the sheet on both sides with a sponge, and then apply the mucilage along the edge, for a width of 1/4-3/8 in. It is a matter of some difficulty to place a sheet upon a board; but if the board is set on its edge, the paper can be applied without assistance.

Then, by putting the strips of paper along the edge, and rubbing over them with some smooth hard instrument, the edges of the sheet can be pasted firmly to the board, the paper slips taking up a part of the moisture from the edges, which are longest in drying. If left in this condition, the centre will dry first, and the paper be pulled loose at the edges by contraction before the paste has time to dry. It is therefore necessary to pass over the centre of the sheet with a wot sponge at intervals to keep the paper slightly damp until the edges adhere firmly, when it can bo left to dry, and will be tight and smooth. One of the most common difficulties in mounting sheets is in not having the gum or gluo thick enough; when thin, it will bo absorbed by the wood or the paper, or is too long in drying. It should be as thick as it can be applied with a brush, and made from clean Arabic gum, tragacanth, or fine glue. Thumb-tacks are of but little use in mechanical drawing except for the most temporary purposes, and may very well be dispensed with altogether; they injure the drawing-boards, obstruct the squares, and disfigure the sheets.