Most of the Enterprise control panels on Star Trek: The Next Generation were made with backlit photographic sheet negatives mounted on sheets of acrylic plastic. In a few cases, the control graphics were silkscreened onto the acrylic. This was a handy trick, since silkscreened panels didn't need to be backlit, which made installation a lot easier, for special effects technicians didn't have to cut holes or put in light bulbs. This also made things easier whenever a director decided, at the last minute, that he or she needed a little control pad on the wall. In such cases, these little panels could simply be stuck up on the wall with adhesive tape, making the director happy, and allowing production to continue undelayed.