The double uni knot is used to join two lines of similar diameter.
Step 1: overlap the two lines side by side, loop one line back away from the other, then back towards it.
Step 2: with the end of the line used to make the loop, wrap both lines, inside the loop 5-6 times as shown.
Step 3: pull tight.
Step 4: repeat steps 1-3 with the other line opposite the first knot.
Step 5: pull lines in opposite directions to join the two knots. Cut loose ends close.
The floatstop knot is used to prevent a float from sliding past a spot on the line. It is small enough to pass through the eyes on a rod, but will hold its place and keep the appropriate depth for float fishing.