A staple for attaching a sheet-like implant to tissue or bone may include first and second arms, and first and second flukes. In some embodiments, the first arm has a proximal end and a distal end, and the second arm has a proximal end and a distal end. A bridge extends from the proximal end of the first arm to the proximal end of the second arm. The first fluke has a proximal end abutting the distal end of the first arm, and the first fluke extends distally from the first arm. The first fluke has a lateral extent larger than a lateral extent of the first arm and is mounted eccentrically thereto. The first fluke includes a proximal surface projecting at an outward angle in a proximal direction away from the distal end of the first arm to engage the tissue or bone when inserted therein. The second fluke has similar features. This arrangement causes the first and second flukes to rotate in response to a pullout force on the bridge. Methods for attaching a sheet-like implant to a target tissue are also disclosed.