A system for deploying a device to a distal location across a diseased vessel, comprising: a railed expandable sheath defining a lumen therethrough and comprising two or more longitudinal rail structures (20, 32, 34) coupled to a sheetlike member, the sheath having a collapsed configuration, wherein the sheath has a first cross sectional outer diameter and a first lumen inner diameter, and an expanded configuration, wherein the sheath has a second cross sectional outer diameter and a second lumen inner diameter; wherein in the collapsed configuration, the sheath is configured to be advanced across at least a portion of the diseased vessel to a position adjacent the distal location without substantial size interference between the first cross sectional outer diameter of the sheath and an inner diameter profile of a lumen of the diseased vessel; and wherein upon positioning the collapsed configuration to the desired position relative to the distal location, the sheath is configured to be expanded to the expanded configuration, such expanded configuration having a diameter greater than said first inner lumen diameter, with incremental pushing of a device, longitudinally through the lumen such that loads imparted upon the sheath by the device are transferred to the rail structures and distributed to nearby portions of the diseased vessel in a deconcentrated and nonabrasive manner; and characterized in that the system further comprises an obturator-jacket assembly configured to assist in temporarily maintaining the collapsed configuration of a distal portion of the sheath, wherein when the obturator-jacket assembly is removed, a proximal portion of the railed sheath remains in a relatively collapsed or small diameter configuration as compared with the expanded distal portion, said distal portion of the sheath features a plurality of the rail structures having a hoop structure coupled to their distal ends, configured to self-expand and to collapse and to support a tubular or frustoconical porous filter mesh surface configured to capture particles that may enter it, such as clots or plaque particles. a railed expandable sheath defining a lumen therethrough and comprising two or more longitudinal rail structures (20, 32, 34) coupled to a sheetlike member, the sheath having a collapsed configuration, wherein the sheath has a first cross sectional outer diameter and a first lumen inner diameter, and an expanded configuration, wherein the sheath has a second cross sectional outer diameter and a second lumen inner diameter; wherein in the collapsed configuration, the sheath is configured to be advanced across at least a portion of the diseased vessel to a position adjacent the distal location without substantial size interference between the first cross sectional outer diameter of the sheath and an inner diameter profile of a lumen of the diseased vessel; and wherein upon positioning the collapsed configuration to the desired position relative to the distal location, the sheath is configured to be expanded to the expanded configuration, such expanded configuration having a diameter greater than said first inner lumen diameter, with incremental pushing of a device, longitudinally through the lumen such that loads imparted upon the sheath by the device are transferred to the rail structures and distributed to nearby portions of the diseased vessel in a deconcentrated and nonabrasive manner; and characterized in that the system further comprises an obturator-jacket assembly configured to assist in temporarily maintaining the collapsed configuration of a distal portion of the sheath, wherein when the obturator-jacket assembly is removed, a proximal portion of the railed sheath remains in a relatively collapsed or small diameter configuration as compared with the expanded distal portion, said distal portion of the sheath features a plurality of the rail structures having a hoop structure coupled to their distal ends, configured to self-expand and to collapse and to support a tubular or frustoconical porous filter mesh surface configured to capture particles that may enter it, such as clots or plaque particles.