THE WORK PRINT is the first print made from the original, usually immediately after the original is processed. It is used for editing the film and as a pattern to which sound tracks are narrated, edited, scored and mixed. When all the editing is completed, the work print is used as the "blueprint" for conforming or matching the original. When the original has been cut to match the work print, both originals and work print are sent to the laboratory as a guide for special effects and for any editing or sound work necessary for completion of the film.
Work prints, which are normally printed on double perforated stock, are usually leadered with double perforated white leader, also called ight struck leader. The leader should be spliced to head and tail or the work print in a matched emulsion position. EMULSION POSITION is a term used to indicate whether the emulsion of the film is on the inside or the outside of a roll. Or, in the case of editing, whether the emulsion of the film is up or down in the synchronizer. (See Fig #1 for leadering in an emulsion up, left-to-right editing setup.) Except for 16mm magnetic sound tracks which will be discussed later and for certain special printing conditions, it is poor film practice to splice head and tail leaders to a film in an unmatched emulsion position. If the emulsion position of the leaders does not match the emulsion position of the film, it is easy to load the film incorrectly into an editing machine, a projector or a laboratory printer. Matching emulsion positions on originals and leaders is vitally important when the film is sent to the lab for printing. If the leaders are spliced in improper emulsion position, the film could be printed backward or damaged during handling.
So splice the leaders on all your picture rolls - beginning with the work print - so that they match the emulsion position of the film - to make it easier for you while you edit and easier for the laboratory to match, time and print.
The leader on the work print should be labeled according to specifications (See Fig. #1) using a permanent type ink.

Work prints are usually labeled and marked for effects on the same side that carries the yellow inked edge numbers. At most laboratories, you may choose to have your numbers placed on either the emulsion or the base side of your work print and original. If you are like most filmmakers, you will want to use the yellow edge numbers as an aid to editing, particularly if you are working with lip sync. For this reason, the side of the work print that the edge numbers go on is normally determined by the editing machine you will be using.
For example, the Moviola calls for the work print to be wound on the reel with the emulsion out. When using a Moviola, the emulsion side will be the side that is up or facing you as you work and will, therefore, be the side on which you will mark your editing cues.
If you are using the Kem or the Steenbeck, you will probably want to ask your laboratory to edge number (also called CODE) your work print on the base side since both of these machines call for the work print be wound base side out. Regardless of which side the yellow numbers are printed on, be sure that you mark fades, dissolves, extended scenes, unintentional splices, etc. on the same side that the yellow numbers are on.
A WORD ABOUT LATENT EDGE NUMBERS (also called KEY NUMBERS): It is not essential to have your work print and original yellow edge numbered. Your film is already numbered by the manufacturer in the sprocket hole area every 20 frames. These numbers are called LATENT or KEY NUMBERS because they are developed along with the latent picture image during processing. NOTE: Professional camera film stocks are the only ones with latent numbers. Films which the manufacturer considers "amateur" - Kodachrome, for example - do not have latent numbers. When the laboratory makes your work print, they will print the original at a wide aperature setting so that the latent numbers on your original are printed onto your work print at no extra charge.
If you prefer to use latent numbers, you should mark the work print on the emulsion side since the latent latent numbers will read right through the emulsion.
Why put the markings on the same side as the yelow numbers or on the side that reads right for the latents? Because the matcher needs all this information readily visible when he is cutting your original to conform to the work print. If your edge numbers are on one side and your effects markings are on another, he will have to twist the film from side to side as he goes to make sure that he is not overlooking some of the instructions you have marked on the work print. This twisting will not only slow him down but it will increase the likely hood of his making an error and miscutting your original. Remember: the matcher does not know your show the way you do - scene by scene or even movement by movement. It is all new to him and he can follow your instructions only if you give him a correct pattern to follw - a properly labeled and marked work print.