Cement splicers join films together by using a chemical called film cement which is made of film base dissolved in a solvent. The Photographic emulsion is removed from the area to be joined and the base of the other end is brought into contact with it.
Film editors use a version with a very small overlaps at the top and bottom of the picture frame to edit film negatives, although units with a longer overlap are preferred for projection release prints.
Here a piece of thin transparent adhesive tape is used to join the two ends. The tape may be pre-perforated for the film perforations, or the splicer may make perforations as the splice is made (this type of splicer is sometimes referred to as guillotine splicer).
Tape splicers can be used on most types of film. This is the most popular way to join polyester prints in theaters.