The Bowline is one of the most useful knots in the world. You can create a loop at the end of a rope that won't get tighter or looser. (bigger or smaller) bowline
Create a large loop and then a small loop. The large loop is the loop you will use to hold onto your work/pipe/rigging. The small loop is for the knot. bowln1
Take the rope end and place up through the small loop. bowln2
Place the end around the long line. bowln3
The end goes back through the small lope. bowln4
Grasp all the parts and tighten. bowln5
The finished knot. bowln6
One of the best things about a Bowline knot is that you can almost always loosen it. The easiest way is pull this loop down along the long line.  bowln7
Like so. Then the rest of the knot will come out. bowln8