An anchor assembly for anchoring a tendon to bone, comprising: a sheath having a substantially solid distal end, at least two sidewalls (112a, 112b) extending proximally from the distal end, the sidewalls (112a, 112b) being separated by at least two slots (114a, 114b) and the sidewalls (112a, 112b) defining an inner lumen therebetween, at least one of anti-plunge tab (1 10a, 1 10b, 110c, 110d) extending from a proximal-most end of the sheath adjacent to at least one of the slots (114a, 114b), the at least one anti-plunge tab (1 10a, 1 10b, 1 10c, 1 10d) preventing over-insertion of the sheath into a bone hole, and at least one retaining tab (108a, 108b, 108c, 108d) extending from the sheath at a location distal to the at least one anti-plunge tab (110a, 110b, 110c, 110d), the at least one retaining tab (108a, 108b, 108c, 108d) being positioned a distance apart from the at least one anti-plunge tab (110a, 110b, 110c, 110d), the distance being configured such that when the at least one anti-plunge tab (110a, 110b, 110c, 110d) is positioned on a proximal surface of a cortical bone, the at least one retaining tab (108a, 108b, 108c, 108d) will extend beneath a distal surface of the cortical bone; and an expander configured to be received between the at least two sidewalls (112a, 112b) on the sheath to cause the sheath to expand and engage bone; characterized in that: the at least one anti-plunge tab (110a, 110b, 110c, 110d) is co-planar with the at least one retaining tab (108a, 108b, 108c, 108d). a sheath having a substantially solid distal end, at least two sidewalls (112a, 112b) extending proximally from the distal end, the sidewalls (112a, 112b) being separated by at least two slots (114a, 114b) and the sidewalls (112a, 112b) defining an inner lumen therebetween, at least one of anti-plunge tab (1 10a, 1 10b, 110c, 110d) extending from a proximal-most end of the sheath adjacent to at least one of the slots (114a, 114b), the at least one anti-plunge tab (1 10a, 1 10b, 1 10c, 1 10d) preventing over-insertion of the sheath into a bone hole, and at least one retaining tab (108a, 108b, 108c, 108d) extending from the sheath at a location distal to the at least one anti-plunge tab (110a, 110b, 110c, 110d), the at least one retaining tab (108a, 108b, 108c, 108d) being positioned a distance apart from the at least one anti-plunge tab (110a, 110b, 110c, 110d), the distance being configured such that when the at least one anti-plunge tab (110a, 110b, 110c, 110d) is positioned on a proximal surface of a cortical bone, the at least one retaining tab (108a, 108b, 108c, 108d) will extend beneath a distal surface of the cortical bone; and a substantially solid distal end, at least two sidewalls (112a, 112b) extending proximally from the distal end, the sidewalls (112a, 112b) being separated by at least two slots (114a, 114b) and the sidewalls (112a, 112b) defining an inner lumen therebetween, at least one of anti-plunge tab (1 10a, 1 10b, 110c, 110d) extending from a proximal-most end of the sheath adjacent to at least one of the slots (114a, 114b), the at least one anti-plunge tab (1 10a, 1 10b, 1 10c, 1 10d) preventing over-insertion of the sheath into a bone hole, and at least one retaining tab (108a, 108b, 108c, 108d) extending from the sheath at a location distal to the at least one anti-plunge tab (110a, 110b, 110c, 110d), the at least one retaining tab (108a, 108b, 108c, 108d) being positioned a distance apart from the at least one anti-plunge tab (110a, 110b, 110c, 110d), the distance being configured such that when the at least one anti-plunge tab (110a, 110b, 110c, 110d) is positioned on a proximal surface of a cortical bone, the at least one retaining tab (108a, 108b, 108c, 108d) will extend beneath a distal surface of the cortical bone; and an expander configured to be received between the at least two sidewalls (112a, 112b) on the sheath to cause the sheath to expand and engage bone; characterized in that: the at least one anti-plunge tab (110a, 110b, 110c, 110d) is co-planar with the at least one retaining tab (108a, 108b, 108c, 108d).