Lay a wooden pallet flat on a work surface with the top facing up. Orient the pallet so that the cross support boards are running horizontally in relation to you. This is the frame for the hanging garden.
Place the three rain gutters on a work surface. Apply plastic gutter cement to the ends of the gutters and to the inside edges of the six gutter caps, using the built-in applicator on the cement container lid. Press the caps onto the ends of the gutters. The cement will form a bond to secure the caps to the ends of the gutter.
Turn the gutters over so that the bottom sides are facing up. Drill a 1/8-inch diameter hole through the center of the bottom of each of the gutters every 2 inches, using a drill equipped with a 1/8-inch drill bit. The holes are for drainage.
Position the gutter hangers on each end of the top, middle and bottom horizontal cross supports on the pallet. Drive the screws that were included with the hangers through the mounting holes into the horizontal cross supports of the pallet using a screw gun.
Center the gutters over pairings of gutter hangers and slide the gutters into the hangers until they lock into place.
Select a position on the exterior structure where you would like to mount the hanging garden. Slide a stud finder along the exterior of the structure and mark the location of two studs at the desired height for the garden using a pencil. Screw one large utility hook into each marked stud location.
Lift the pallet up and hang the top horizontal cross support on the back of the pallet over the two large utility hooks. Fill each gutter length with potting soil using a trowel.