The legs need to be fitted approximately one inch down from the top of the Fender Twin. Use a measuring tape to mark the position accurately. Mark the spots to drill holes for the legs on either side of the amplifier. Make sure both holes are at exactly the same measurement on either side.
To securely fit the legs to the Fender Twin, use a drill to bore holes at the marked spots on the sides of the amplifier. A screwdriver can then be used to screw the legs to the side of the amplifier. A washer will be needed to secure the leg fitting and enable the legs to move into the tilt-back position.
The legs should also have rubber feet on the bottom to keep them from marking the floor. This will also prevent them from slipping on smooth surfaces, keeping the amplifier secure in a tilt-back position.