Slide Black Knight into your VCR or DVD player only if you’re feeling drowsy. Martin Lawrence, playing modern man gone medieval, will be just the boring, warm milk to put you to sleep. The unchivalrous Lawrence accidentally jumps to the 14th century and ends up battling an evil king, wooing a lovely chambermaid, and saving England. The plot turns shouldn’t surprise anyone who’s ever seen a movie before. If you must, see ”Knight” to chuckle at Tom Wilkinson, whose presence here is a reminder of some of the questionable parts he accepted before his Oscar-nominated In the Bedroom role.