I also stick a pin through in different areas to see where its going to line up on the other side.

What I do is tape a few toothpicks vertically along the center line of the table. Then I fold the backing in half and put single basting stitches in an X at 12" intervals along the fold. I can get by with not pressing the fold into the backing that way. I line up the X's over the toothpick center line, and clamp the backing to the table. I double-check that I'm in the middle by measuring. After the batting and top are on, I can usually figure from the design where the middle is, but i can also feel the toothpicks, too. Of course, my table is sort of narrow, which probably makes a difference.

Charlotte, hoping that makes sense

Oh you are so smart. Don't think I would ever thought of this. Guess this old dog can learn new tricks. Thanks.

I use either a pin or those red clips at centre of each side . Match and go?if using any other methods I found you need to start with middle
One and the then roll out .