Why? ......... a contact sheet is used by photographers to preview a number of pictures that were taken during a "shoot" . Usually only those pictures that are considered of value are then processed saving time and money.
The contact sheet also serves as a way to organize and archive a large number of images.

You may offer a client  the contact sheet as proof of your on going work as well as allow your client to pick the photos they will pay for.
(don't be surprised when they are not the ones you would have chosen!)

They may help in the selection process when working on a team project.

In film photography the contact prints are limited to the size of the film (35mm) as the contacts are made by placing the negatives on photographic paper and then exposed.

In digital photography the computer and software are the darkroom and thus contact sheets can be made with contact images of a size you want

How? ....... various softwares offer excellent ways to create a variety of contact sheets we will use PhotoShop.

> OPEN PhotoShop
> File > Automate > Contact Sheet
> select your Photo Directory (where your digital image files are located )
> select the number of rows and columns for the contact sheet
> OK and the contact sheet(s) will be produced automatically
> Save for Web and post your contact sheet(s)
> SAVE FOR WEB and then place your contacts on your portfolio