1. In a large bowl, mash the blackberries and add the pectin.
2. Pour into a large pot and heat until boiling. Add the sugar.
3. Bring back to a boil then remove from heat.
4. Ladle into sterilized jars, leaving 1/4 inch room at the top. Put the lids on the jars and place in a hot water bath (be sure the tops of the jars are covered with about one inch of water). Bring to a boil and continue boiling for 5 minutes.
5. Remove from the boiling water bath and let sit overnight.

Prep time is 1.5 hours, including picking the berries :)

If you live above sea level, you will need to adjust the time in the boiling water bath. At 1,000-6,000 feet altitude, boil for 10 minutes; above 6,000 feet altitude, boil for 15 minutes.