FORMS In general, wood will be used for the forms, though thin strips of metal will be found con venient in forming curved lines. Also, the use of a metal cross-form or parting strip will be a guarantee against defects arising from imper fect joints or expansion. The cross-form should be made of metal, with stiffeners of the same thickness on the ends and top. Wedges are to be driven from the outside into the 1/2-inch clearance space between the wooden side forms and the metal cross-form. Ready-made parting strips of special patented type are now on the market.
The wooden forms should be constructed of clean lumber free from warp, and at least 2 inches thick by about 5 inches wide. Surfaced lumber has advantages, but its use is not necessary.
In placing the side forms along the line of the walk, care should be taken to maintain a good alignment, and they should be leveled so as to conform with the finished grade.
Providing for Surface Drainage of Walk. The form nearest the street should be slightly below the inside form, thus providing a drain which will prevent water from collecting on the walk. The side forms should be securely staked, the stakes alternating on either side about every two feet. If the special metal cross-form is used, fewer stakes will answer, for when the form is keyed into position, it is rigidly fastened and holds the outside forms in their proper rela tive position. Wooden cross-forms need only be
held in place by stakes on the opposite side from which the concrete is to be deposited. When the concrete is being placed, a shovelful or two will hold the cross-forms firmly until it is tamped into position.
When wooden cross-forms are used, the loca tion of the joints should be definitely determined and plainly marked on the side forms before any concrete is placed. The cross-forms should be placed so that the face against which the con crete is to be packed is in line with the points indicating the position of the joints.