CBS will move Twentieth TV’s first-year drama “Picket Fences” to Thursday nights starting in April and bring back the David Jacobs-Lorimar TV summer series “Bodies of Evidence” in “Fences’ ” current slot at 10 p.m. Fridays as of April 2.The move sets up a scenario in which “Fences” exec producer-creator David E. Kelley will face off at 10 p.m. Thursdays against his old Twentieth series, “L.A. Law,” which will return from a March hiatus with new episodes overseen by another “Law” alumnus, William M. Finkelstein. The shift also will give the network a chance to evaluate the critically lauded “Fences” in a different, higher-profile slot and establishes the series as a candidate to replace longtime slot occupant “Knots Landing,” which will complete its 14-year run after this season. “Knots” will air its last regular episode in March and conclude with a two-hour finale held back for the May sweeps (Daily Variety, Jan. 11). “Evidence,” which stars Lee Horsley as a homicide cop, performed well in the “Knots” slot during a trial stint last summer, averaging a 10.3 rating, 18 share in Nielsen despite lower HUT (homes using TV) levels in the summer and stiff competition from the Summer Olympics. Network officials believe the show has a chance of holding its own in the Friday slot opposite news magazine “20/20″ and NBC’s lineup, which usually consists of repeat “Perry Mason” movies. CBS has tried repeatedly to boost exposure for “Fences,” including a couple of Monday airings in “Northern Exposure’s” slot.