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 (600a, 600b) 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 (586a, 586b) of each of the first and second rail bottom portions (582a, 582b), 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 (600a, 600b) 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 (586a, 586b) of each of the first and second rail bottom portions (582a, 582b), 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.