PROBLEM TO BE SOLVED: To provide a pressure-activated cloth seal either for the static use or the dynamic use. SOLUTION: The seal assembly comprises a cloth seal for sealing a cavity 75 between a first engagement body 70 and a second engagement body 80. The seal divides the cavity 75 into a high pressure region PH and a low pressure region PL, and has a shim assemblage 64 and a cloth assemblage 62. A first peripheral part of the cloth seal may include a part of the cloth assemblage 62 and/or the shim assemblage 64 in contact with the high pressure region PH, and a second peripheral part may include a part of the cloth assemblage 62 in contact with the low pressure region PL. Therefore, by knowing the condition of the flow and the difference of pressure passing through the seal, the density of the cloth seal can be calibrated to control the leakage and in addition, the shim and cloth assemblages can be designed so that the contact load on the engagement bodies will be minimized.