A building system comprising: a building surface comprising a plurality of interconnected panels wherein adjacent panels are interconnected to define a standing seam; a mounting device positioned on the building surface, the mounting device comprising: a first end opposite a second end, the first end spaced apart from the second end by a first length; an upper wall disposed above and spaced from an underlying portion of said building surface; an un-threaded mounting slot that extends through said upper wall and that is elongated in a first dimension; a nut receptacle that is disposed below and aligned with said mounting slot, wherein the nut receptacle: has a minimum width greater than a maximum width of the un-threaded mounting slot; extends from the first end to the second end; is located between the building surface and the mounting slot; is accessible from the first end, the second end, and the un-threaded mounting slot; and is defined at least in part by a pair of base surfaces (263b, 263d) that are disposed in opposing relation and that are spaced from each other to limit rotation of a nut within the nut receptacle, each base surface of the pair of base surfaces being associated with a flat on a sidewall of the nut; and a bottom surface opposite to the upper wall; wherein the mounting device further comprises a slot on the bottom surface to receive at least a portion of a standing seam, the slot extending between the first and second ends; and a threaded hole extending through the mounting device to the slot; wherein the building system further comprises a first fastener directed through the threaded hole and into the slot to engage the standing seam, wherein the first fastener is engaged with each of the building surface and the mounting device to maintain the mounting device in a fixed position relative to the building surface; and an attachment fastener comprising a head and a shaft extending from the mounting slot, threadably engaged with the nut, the head and nut movable relative to one another to maintain the attachment fastener in a fixed position relative to the mounting device and to secure an attachment to the mounting device, wherein at least part of the nut is retained within the nut receptacle by a configuration of the nut receptacle but the nut is still movable along the nut receptacle in the first dimension, wherein the attachment fastener is disposable in multiple positions along the mounting slot and in the first dimension, and wherein the attachment fastener is threadably engageable with the nut in each of the multiple positions. a building surface comprising a plurality of interconnected panels wherein adjacent panels are interconnected to define a standing seam; a mounting device positioned on the building surface, the mounting device comprising: a first end opposite a second end, the first end spaced apart from the second end by a first length; an upper wall disposed above and spaced from an underlying portion of said building surface; an un-threaded mounting slot that extends through said upper wall and that is elongated in a first dimension; a nut receptacle that is disposed below and aligned with said mounting slot, a first end opposite a second end, the first end spaced apart from the second end by a first length; an upper wall disposed above and spaced from an underlying portion of said building surface; an un-threaded mounting slot that extends through said upper wall and that is elongated in a first dimension; a nut receptacle that is disposed below and aligned with said mounting slot, has a minimum width greater than a maximum width of the un-threaded mounting slot; extends from the first end to the second end; is located between the building surface and the mounting slot; is accessible from the first end, the second end, and the un-threaded mounting slot; and is defined at least in part by a pair of base surfaces (263b, 263d) that are disposed in opposing relation and that are spaced from each other to limit rotation of a nut within the nut receptacle, each base surface of the pair of base surfaces being associated with a flat on a sidewall of the nut; and a bottom surface opposite to the upper wall; wherein the mounting device further comprises a slot on the bottom surface to receive at least a portion of a standing seam, the slot extending between the first and second ends; and a threaded hole extending through the mounting device to the slot; wherein the building system further comprises a first fastener directed through the threaded hole and into the slot to engage the standing seam, wherein the first fastener is engaged with each of the building surface and the mounting device to maintain the mounting device in a fixed position relative to the building surface; and an attachment fastener comprising a head and a shaft extending from the mounting slot, threadably engaged with the nut, the head and nut movable relative to one another to maintain the attachment fastener in a fixed position relative to the mounting device and to secure an attachment to the mounting device, wherein at least part of the nut is retained within the nut receptacle by a configuration of the nut receptacle but the nut is still movable along the nut receptacle in the first dimension, wherein the attachment fastener is disposable in multiple positions along the mounting slot and in the first dimension, and wherein the attachment fastener is threadably engageable with the nut in each of the multiple positions.