A fastener cartridge, comprising: a cartridge body, comprising: a deck; fastener cavities defined in said deck, wherein each said fastener cavity comprises a proximal end and a distal end; proximal projections extending from said deck, wherein each said proximal projection is positioned at a said proximal end of a said fastener cavity; and distal projections extending from said deck, wherein each said distal projection is positioned at a said distal end of a said fastener cavity; fasteners removably stored in said fastener cavities; a layer of material supported by said deck, comprising: a layer body; proximal apertures defined in said layer body, wherein each said proximal aperture is configured to receive a said proximal projection; and distal apertures defined in said layer body, wherein each said distal aperture is configured to receive a said distal projection; wherein said distal projections and said distal apertures are sized and configured such that there is an interference fit therebetween, wherein said proximal projections and said proximal apertures are sized and configured such that there is an interference fit therebetween, and wherein said interference fits releasably retain said layer of material to said cartridge body; characterized in that said proximal apertures and said distal apertures comprise through holes. a cartridge body, comprising: a deck; fastener cavities defined in said deck, wherein each said fastener cavity comprises a proximal end and a distal end; proximal projections extending from said deck, wherein each said proximal projection is positioned at a said proximal end of a said fastener cavity; and distal projections extending from said deck, wherein each said distal projection is positioned at a said distal end of a said fastener cavity; a deck; fastener cavities defined in said deck, wherein each said fastener cavity comprises a proximal end and a distal end; proximal projections extending from said deck, wherein each said proximal projection is positioned at a said proximal end of a said fastener cavity; and distal projections extending from said deck, wherein each said distal projection is positioned at a said distal end of a said fastener cavity; fasteners removably stored in said fastener cavities; a layer of material supported by said deck, comprising: a layer body; proximal apertures defined in said layer body, wherein each said proximal aperture is configured to receive a said proximal projection; and distal apertures defined in said layer body, wherein each said distal aperture is configured to receive a said distal projection; a layer body; proximal apertures defined in said layer body, wherein each said proximal aperture is configured to receive a said proximal projection; and distal apertures defined in said layer body, wherein each said distal aperture is configured to receive a said distal projection; wherein said distal projections and said distal apertures are sized and configured such that there is an interference fit therebetween, wherein said proximal projections and said proximal apertures are sized and configured such that there is an interference fit therebetween, and wherein said interference fits releasably retain said layer of material to said cartridge body; characterized in that said proximal apertures and said distal apertures comprise through holes.