A method of using a shape-formable apparatus, the method comprising: providing a shape-formable apparatus in a first state in which the apparatus is formable, the shape-formable apparatus comprising: an envelope (102, 202) defining a chamber, the envelope formed of a gas-impermeable material; a port positioned to fluidly couple the chamber with ambience; a fibrous material positioned in the chamber; and a locking sheet positioned adjacent the fibrous material in the chamber, the locking sheet comprising a major surface, and wherein at least a portion of the locking sheet is patterned to include solid regions and open regions, the solid regions being movable with respect to one another within the major surface, forming the apparatus into a desired shape when the apparatus is in the first state; and reducing the pressure in the chamber to change the apparatus from the first state to a second state in which the apparatus has the desired shape and is substantially less formable than in the first state, wherein the fibrous material includes at least one fiber, and wherein forming the apparatus into a desired shape includes at least one of: moving portions of a fiber relative to one another within the fibrous material, and moving fibers relative to one another within the fibrous material. providing a shape-formable apparatus in a first state in which the apparatus is formable, the shape-formable apparatus comprising: an envelope (102, 202) defining a chamber, the envelope formed of a gas-impermeable material; a port positioned to fluidly couple the chamber with ambience; a fibrous material positioned in the chamber; and a locking sheet positioned adjacent the fibrous material in the chamber, the locking sheet comprising a major surface, and wherein at least a portion of the locking sheet is patterned to include solid regions and open regions, the solid regions being movable with respect to one another within the major surface, an envelope (102, 202) defining a chamber, the envelope formed of a gas-impermeable material; a port positioned to fluidly couple the chamber with ambience; a fibrous material positioned in the chamber; and a locking sheet positioned adjacent the fibrous material in the chamber, the locking sheet comprising a major surface, and wherein at least a portion of the locking sheet is patterned to include solid regions and open regions, the solid regions being movable with respect to one another within the major surface, forming the apparatus into a desired shape when the apparatus is in the first state; and reducing the pressure in the chamber to change the apparatus from the first state to a second state in which the apparatus has the desired shape and is substantially less formable than in the first state, wherein the fibrous material includes at least one fiber, and wherein forming the apparatus into a desired shape includes at least one of: moving portions of a fiber relative to one another within the fibrous material, and moving fibers relative to one another within the fibrous material. moving portions of a fiber relative to one another within the fibrous material, and moving fibers relative to one another within the fibrous material.