Building stop to check TDC

Set the piston stop so it hits some about before TDC say 20 Degrees make a mark on the harmonic balancer at the 0 Timing point on your degree indicator. Back the engine around the other way till you the other side of TDC, make another mark...right in between them should be exactly TDC. I've also just done it with a piece a wire down the spark plug hole just feeling when it stops coming up...which is kind of redneck but it can get pretty close.