I assume you are referencing a photo holder in relation to your CHL application;
It is what the passport photos attach to. For a while, DPS just had the applicant put the photos in an envelope. An instructor shoule be able to get you one.
TI :: Well as far as I know , we are back to using envelopes again. Instructions in the last packets had it that way. I just got a new box of packets but have not looked to see if we are back to holders.
Tanker: Don't sweat it, if you don't have a holder just put the photos in an envelope. Make sure your photos are signed by you and the person taking your prints. Write your name and DL number on the outside of the envelope and Write"Photos Enclosed" on it also. It will be fine, like Adionik mentioned be sure to fill out the Passport photo sheet and put your signature in the yellow box at the bottom of the page. DO NOT GO OUTSIDE THE LINES OF THE BOX.