A compression-self-adjusting staple (20, 30, 40, 50, 60, 70, 80, 90, 100, 110, 120, 130, 140, 150, 160), comprising: a substantially U-shaped staple (20, 30, 40, 50, 60, 70, 80, 90, 100, 110) having: legs (26, 32, 42, 52, 62, 72, 82, 92, 102, 112); a bridge (21, 31, 41, 51, 61, 71, 81, 91, 101, 111) connecting the legs; and a compression device (23, 23, 43, 53, 63, 73, 83, 93, 103, 113, 123, 133, 143, 153, 163): at least partly disposed between the legs (26, 32, 42, 52, 62, 72, 82, 92, 102, 112); having a bias portion (25, 34, 44, 54, 64, 74, 84, 94, 104, 114, 124, 134, 144) with: a compression surface movably disposed between the legs (26, 32, 42, 52, 62, 72, 82, 92, 102, 112); and a compression resistor: connected with the bridge (21, 31, 41, 51, 61, 71, 81, 91, 101, 111, 121, 131, 141, 151, 161) and with the compression surface; and being formed to resist movement of the compression surface towards the bridge (21, 31, 41, 51, 61, 71, 81, 91, 101, 111, 121, 131, 141, 151, 161) with a force; and characterised byhaving a variation in cross-section including at least one of a variation in cross-section shape and a variation in cross-section thickness. legs (26, 32, 42, 52, 62, 72, 82, 92, 102, 112); a bridge (21, 31, 41, 51, 61, 71, 81, 91, 101, 111) connecting the legs; and a compression device (23, 23, 43, 53, 63, 73, 83, 93, 103, 113, 123, 133, 143, 153, 163): at least partly disposed between the legs (26, 32, 42, 52, 62, 72, 82, 92, 102, 112); having a bias portion (25, 34, 44, 54, 64, 74, 84, 94, 104, 114, 124, 134, 144) with: a compression surface movably disposed between the legs (26, 32, 42, 52, 62, 72, 82, 92, 102, 112); and a compression resistor: connected with the bridge (21, 31, 41, 51, 61, 71, 81, 91, 101, 111, 121, 131, 141, 151, 161) and with the compression surface; and being formed to resist movement of the compression surface towards the bridge (21, 31, 41, 51, 61, 71, 81, 91, 101, 111, 121, 131, 141, 151, 161) with a force; and characterised byhaving a variation in cross-section including at least one of a variation in cross-section shape and a variation in cross-section thickness. at least partly disposed between the legs (26, 32, 42, 52, 62, 72, 82, 92, 102, 112); having a bias portion (25, 34, 44, 54, 64, 74, 84, 94, 104, 114, 124, 134, 144) with: a compression surface movably disposed between the legs (26, 32, 42, 52, 62, 72, 82, 92, 102, 112); and a compression resistor: connected with the bridge (21, 31, 41, 51, 61, 71, 81, 91, 101, 111, 121, 131, 141, 151, 161) and with the compression surface; and being formed to resist movement of the compression surface towards the bridge (21, 31, 41, 51, 61, 71, 81, 91, 101, 111, 121, 131, 141, 151, 161) with a force; and characterised byhaving a variation in cross-section including at least one of a variation in cross-section shape and a variation in cross-section thickness. a compression surface movably disposed between the legs (26, 32, 42, 52, 62, 72, 82, 92, 102, 112); and a compression resistor: connected with the bridge (21, 31, 41, 51, 61, 71, 81, 91, 101, 111, 121, 131, 141, 151, 161) and with the compression surface; and being formed to resist movement of the compression surface towards the bridge (21, 31, 41, 51, 61, 71, 81, 91, 101, 111, 121, 131, 141, 151, 161) with a force; and characterised byhaving a variation in cross-section including at least one of a variation in cross-section shape and a variation in cross-section thickness. connected with the bridge (21, 31, 41, 51, 61, 71, 81, 91, 101, 111, 121, 131, 141, 151, 161) and with the compression surface; and being formed to resist movement of the compression surface towards the bridge (21, 31, 41, 51, 61, 71, 81, 91, 101, 111, 121, 131, 141, 151, 161) with a force; and characterised byhaving a variation in cross-section including at least one of a variation in cross-section shape and a variation in cross-section thickness.