 This flexible frame, which is used in addition to the decorative frame described below, exerts pressure on the panel to keep it from warping further.In 1970, the beech crosspieces were switched to maple after it was found that the beechwood had been infested with insects.In 2004–05, a conservation and study team replaced the maple crosspieces with sycamore ones, and an additional metal crosspiece was added for scientific measurement of the panel's warp.