Video and Step-by-Step Installation Instructions:
Classic Return Air Filter Box  — Assembly Instructions via YouTube video:

Classic Return Air Box Assembly — Written Instructions (<5 mins per box to assemble when proficient):
Classic Air Box is shipped flat and requires assembly (we have options for pre-assembly and shipping, too, just call us!). Screws are included. Filter is not included.

WARNING! Sharp Edges GLOVES REQUIRED

Tools: 

• Rubber Mallet or Hammer (for connecting metal pieces together!)
• #2 Philips Bit on Drill (for attaching self-tapping screws)
• Pliers or Putty knife or flathead screwdriver (for bending tabs)
• Gloves (for safety from sharp metal)

In the box:

2x Side Panels, 1x rear panel, 1x front panel, 1x base panel, 1x filter holder, 2x filter rails, 7x self-tapping screws

Step 1: Attach the rear panel to the side panels by pushing the metal parts together and using a rubber mallet to pound in each of the corners. Attached the front panel using same method. At end of this step the four sides of the box are standing.

Step 2: In the upper corners of the box, on each of the four corners, screw in a self-tapping screw to hold the box together.

Step 3: Flip the box upside down and push in the upper, filter holder piece.

Step 4: Secure the filter holder to the base by using 2x screws on the front panel, and 1x screw in the middle on the back panel.

Step 5: Push to fit each filter rail into the upper holder, one on each side.

Step 6: Install the base piece and fit over the metal edges. Once fit into place, locate the anchor tabs in each corner of the base and bend them over. This secures the base to the box. Use pliers to bend or using any tool with a wide/flat blade (scraper tool, blade tool, flathead screwdriver).
The assembly is complete and is ready to be installed with the rest of the furnace.