Saddlestitched booklets are booklets that are bound with a staple on the spine (the folded edge). Multiple sheets are scored, folded in half, collated, and then stapled to create the booklet. The page count of saddlestitched booklets is always a multiple of 4.
Saddlestitched booklets can be produced as self cover where the cover stock matches the inside pages or with a hard cover where the cover stock is thicker than the inside pages. Depending on the stocks used, this booklet type is generally used for smaller booklets with page counts of 100 pages or less (based on a 50lb uncoated self-cover booklet).