A rail assembly attachable to a building surface , wherein the rail assembly comprises a rail that in turn comprises a one-piece body, wherein the one-piece body comprises: a rail top comprising an attachment fastener slot that extends along an entire length of the one-piece body that is within a longitudinal dimension ; a rail bottom that is spaced from the rail top in a vertical dimension ; a first rail side comprising a first rail channel that extends along the entire length of the one-piece body; a second rail side comprising a second rail channel that extends along the entire length of the one-piece body, wherein the first and second rail sides are spaced from one another in a lateral dimension that is orthogonal to the longitudinal dimension; a first pocket having a closed perimeter and that extends along the entire length of the one-piece body, wherein a first rail bottom portion of the rail bottom defines a lower extreme of the first pocket ; a second pocket having a closed perimeter and that extends along the entire length of the one-piece body, wherein a second rail bottom portion of the rail bottom defines a lower extreme of the second pocket ; and a third pocket that is disposed between the first pocket and the second pocket in the lateral dimension and that extends along the entire length of the one-piece body, wherein the attachment fastener slot extends to and intersects the third pocket , wherein a third rail bottom portion of the rail bottom defines a lower extreme of the third pocket , wherein a lower surface of the third rail bottom portion is recessed in a direction of the rail top relative to a lower surface of each of the first and second rail bottom portions , wherein the first rail channel is adjacent to but isolated from the first pocket , and wherein the second rail channel is adjacent to but isolated from the second pocket . a rail top comprising an attachment fastener slot that extends along an entire length of the one-piece body that is within a longitudinal dimension ; a rail bottom that is spaced from the rail top in a vertical dimension ; a first rail side comprising a first rail channel that extends along the entire length of the one-piece body; a second rail side comprising a second rail channel that extends along the entire length of the one-piece body, wherein the first and second rail sides are spaced from one another in a lateral dimension that is orthogonal to the longitudinal dimension; a first pocket having a closed perimeter and that extends along the entire length of the one-piece body, wherein a first rail bottom portion of the rail bottom defines a lower extreme of the first pocket ; a second pocket having a closed perimeter and that extends along the entire length of the one-piece body, wherein a second rail bottom portion of the rail bottom defines a lower extreme of the second pocket ; and a third pocket that is disposed between the first pocket and the second pocket in the lateral dimension and that extends along the entire length of the one-piece body, wherein the attachment fastener slot extends to and intersects the third pocket , wherein a third rail bottom portion of the rail bottom defines a lower extreme of the third pocket , wherein a lower surface of the third rail bottom portion is recessed in a direction of the rail top relative to a lower surface of each of the first and second rail bottom portions , wherein the first rail channel is adjacent to but isolated from the first pocket , and wherein the second rail channel is adjacent to but isolated from the second pocket . <EOS>