Built this adjustable sandbox shade/cover using 3/4" EMT conduit and Maker Pipe parts. The vertical posts are 6'6" and secured to the sandbox using the flange connector. (For added strength, I used threaded inserts and washers secured with a 1/4-20 bolt on each flange, as seen here: https://youtu.be/T3fltP7HRM8?t=322). The horizontal pieces up top are secured to the vertical beams using the 90 degree connector piece.

I used this shade from Amazon: https://www.amazon.com/dp/B08PD7L96B?ref_=cm_sw_r_cp_ud_dp_32A5ZAGFBZ1411VTE2XS . The shade is attached to the vertical posts loosely using parachute cord; this allows the shade to be raised and lowered along the vertical posts so that it can function as a cover when the sandbox isn't being used. Along the horizontal posts, I have attached 8 6" bungees (https://www.amazon.com/dp/B098NHTVGH?ref_=cm_sw_r_cp_ud_dp_6KH9AE5X45TZFMM3QHBY) that clip into the grommets on the side of the shade to hold it in the up position. To angle the shade, the desired bungees can be detached and the shade pulled down to the appropriate angle.

The sand box was built using this simple design: https://www.thisoldhouse.com/yards/21016649/how-to-build-a-simple-sandbox