A flat form is single copy form prepared manually or by a machine and printed on any grade of paper. For additional copies of the original, carbon paper is inserted between copies. It is the easiest form to design, print, and reproduce; it has a low-volume use; and it is the least expensive. Often a pad of the flat forms is printed identical to the original copy of a unit set.
2.Unit-set/Snap out forms:
These forms have an original copy and several copies with one–time carbon paper interleaved between them. The set is glued into a unit for easy handling. The carbon paper is approximately 3/8 inch shorter than the copies. The copies are perforated at the glue margin for tearing out, although the carbon is not perforated. Because of the perforation and the shorter carbon, the forms can be easily snapped out after completion.
3.Continuous strip/fanfold forms:
These are multiple – unit forms joined together in a continuous strip with perforations between each pair of forms. One–time carbon is inter-leaved between copies, which are stacked in a fanfold arrangement. The fanfold is the least expensive construction for large volume use. Computer printouts are invariably produced on them; they are virtually part of system design.
4.NCR (no carbon Required) paper:
Several copies can be made by pressing a chemical undercoating on the top sheet into a claylike coating on the top of the second sheet. The writing pressure forms an image by the coating material. The same process applies to the back of the second sheet for producing a carbon copy on the face of the succeeding sheet, and so on. It offers cleaner and long-lasting copies. One problem with NCR is the sensitivity of chemicals. It shows every scratch. It is costly.