I don't use a canner to seal my jars. This is how my Great Aunt taught me to seal jars. This only works for cooked jam and jelly recipes.
First, as I am making my Jam, I heat up a 2 pans of water. 1 with enough water to cover the jars laying down. When the jam is almost done cooking, I carefully add the clean jars to the boiling water.
After, I remove the jam from the direct heat, I place a towel in my left hand and use tongs to remove a jar from the boiling water.
Be very careful, the jar is very hot!!!
This is where I add 1 lid to the boiling water in small sauce pan.
Carefully, ladle the jam into the jar. (Sorry, my kitchen counter is cluttered. It usually is when I am making jam.)
Fill the jar up to a 1/2" from the top and carefully wipe off the excess jam that dripped over the edge. I use a towel or clean dishcloth.
Take the lid out of the boiling water and place lid on top of jar.
Screw rim on jar tightly.
Place jar on dish towel and cover jars with another dish towel.
In the next few hours, you will start to hear the lids popping/sealing shut. If they don't seal, (which I have never have had happen) toss the old lid, and start the process over again.