Disclaimer: I’d like to make sure it’s understood that these are in no way to be taken as qualified instruction. I suppose that technically I should classify these as ‘reminders’, but it is possible to learn from them… Just make sure you check with someone that actually knows what they’re doing before you try and do them halfway up a cliff.
Extra disclaimer: The bowline is a potentially dangerous knot; if tied incorrectly, it will not work at all. The reason we teach the figure of 8 for tying in is that it’s absolutely bombproof. Even if you get it slightly wrong, it’ll almost certainly still function. If you ever use this knot, be sure you’ve tied it right before you commit to it.
The Yosemite bowline is a particular type of re-threading of a bowline, often used for sport climbing. If ‘dressed’ (the way the knot sits when tightened) correctly, it adds to the strength of the knot, but under extreme circumstances it can work free into a slip knot that should still hold a fall, but… yeah. (The reason for this is that when you re-thread it in this way, you actually undo one of the parts of the bowline, but it’s not noticeable unless it inverts and gets pulled in a certain way.)
Start by tying a standard bowline.
Pass the tail through the back of the rope loop, then back through the front and up through the distinctive loop of the bowline.
You should end up with what looks like a second turn on the lower half of the knot, like so:
Now, finish off with a stopper knot above the bowline.