Clean and sanitize containers.

Strain rinsed, ripe blackberries over a large bowl by mashing with a wooden spoon against the strainer.

Measure exactly 3 cups of mashed and/or strained blackberries into a large bowl.

Measure exactly 5 1/4 cups sugar (do not reduce sugar or use a substitute - it won't set up)

Let sugar and berries stand for 10 minutes, stirring occasionally.

Stir 1 package Sure Jell pectin and 3/4 cup water in a small saucepan. Bring to a boil on high heat, stirring constantly. Boil 1 minute, stirring constantly. Remove from heat.

Add pectin mixture to blackberry/sugar mixture. Stir for 3 minutes or until sugar is dissolved and no longer grainy.

Fill containers immediately, leaving 1/2 inch space at the top for expansion. Wipe up any spills around the top of the containers. Cover with lids.

Let stand at room temperature 24 hours. Refrigerate up to 3 weeks or freeze for up to a year. If frozen, thaw in fridge before using.