The Dropper Loop (also known as both a blood loop and a snood loop) is designed to stand off from the line at 90 degrees - and therein lies the problem.
No line likes a sharp bend like this - it will always create internal stresses resulting in an inherent weakness.
There are several versions of this knot, but the one described here is one of the strongest.
As an alternative you could use a 3-way swivel, attaching the lines with Uni-Knots.
Stage 1
Stage 2
Then, pass it through the gap shown so it looks like this. Now take the top of the loop formed and pass it through the square gap shown.
Stage 3
Stage 4
Finally, lubricate with saliva and draw the knot up tight. Attach your hook link to it by cow-hitching the two loops together.
If you like the idea of having the most popular sea fishing knots all together in one place for easy reference, this handy little pocket guide is just the thing.
It sets out in step-by-step instructions and nicely drawn sketches how to tie all the knots you'll ever be likely to need - 18 of them in all.
Being spiral bound it opens flat, leaving both hands free to tie the knot - and it's waterproof!
Connecting Hooks, Swivels and Lures to Single-Strand Wire Line
Forming a Stand-Off dropper Loop in Mono Line
Forming a Reinforced Loop in Mono Line
Connecting Mono Line Directly to Single-Strand Wire Line