Richard Karn (L) and Tim Allen reunite to host "Assembly Required." Photo courtesy of History Channel Richard Karn (L) and Tim Allen try out flamethrowers on "Assembly Required." Photo courtesy of History Channel Tim Allen hosts "Assembly Required" on the History Channel. File Photo by Jim Ruymen/UPI | License Photo LOS ANGELES, Feb. 23 (UPI) -- Tim Allen and Richard Karn, who played co-hosts of fictional show Tool Time on Assembly Required -- as much the same characters. "This is an expansion of that relationship," Allen said on a recent Television Critics Association Zoom panel ahead of Tuesday's premiere. "We're very similar to the characters we play in that show."