Single Roll: A single roll of wallpaper that measures (typically) 27 inches in width and 5 yards long.

Double roll: A double roll is the equivalent length of two single rolls on one physical roll.

Dye Lot: Bolts of the same wallpaper pattern that were manufactured at the same time. Occasionally "dye lots" may vary slightly. 

Half Drop: Specific to wallpaper, the half drop is where the pattern repeats across the roll half way down the vertical repeat. This normally means allowing for extra length and cutting very carefully as each cut will start at the half repeat. The best way to be certain of buying enough wallpaper, is to work it out as if it were an ordinary repeat and add half a repeat to each drop, except for the first one. 

Matching: The technique of joining two strips of wallpaper so that partial designs or a sequence of designs line up properly. 

Memo: (Synonymous with "sample") A small piece of wallpaper from a selected pattern. This may or may not be from the bolt of wallpaper a customer will receive. Samples show general color and texture of the pattern. 

Repeat: The pattern repeat is the vertical distance between where the pattern is identical again (repeats). That distance can be less than an inch or as much as the entire width of the wallpaper. 

Reserve: Wallpaper that is reserved for a customer. This ensures the customer of having a specific wallpaper available until the purchase is made. 

Sample: (Synonymous with "memo") A small piece of wallpaper from a selected pattern. This may or may not be from the bolt of wallpaper a customer will receive. Samples show general color and texture of the pattern.