3. First lock the 4 screws on the corner connectors, then take out 4 pieces of M5
nuts and put 2 in the groove of each side of the frame.
4. First, take out 2 pieces of corner connectors and 1 pieces of aluminum profile
with length of 540mm, load the corner codes into the aluminum profile, and then
take out 2 pieces of M5*25 screws to fix the aluminum profile.