Patent ID: 8511002

Claim:
A bridge comprising, in combination: a steel structure forming an enclosed space and forming an opening providing access to the enclosed space; a sheet sized to cover the opening and to at least partially overlap the steel structure at the opening; wherein the sheet has a plurality of spaced-apart holes sized sufficiently large to permit passage of air and water therethrough and sized sufficiently small to prevent passage of pigeons therethrough; wherein the sheet includes a magnetic portion for magnetically securing the sheet to the steel structure; wherein the sheet is sufficiently flexible to be selectively removed from the steel structure at one side of the opening, folded upon itself, and secured to the steel structure at an opposite side of the opening so that the sheet remains secured to and supported by the steel structure at the opposite side of the opening in a retracted configuration when it is desired to have access through the opening; and wherein the steel structure is a truss bridge having at least two members forming an acute angle therebetween and the sheet is secured between the two members and is flexible enough that the sheet is partially folded and curved between the two members when covering the opening.