Here’s the video, which should help clarify things:
I wouldn’t have bruised and blackened my toenails last week if I had taken the time to employ one of my favorite hiking boot lacing techniques: the heel lock. It’s best illustrated visually (the video above does a good job of demonstrating the technique), but here’s essentially how it works.
First, lace your boots snugly over the top of your foot (the instep), but not so tight that it restricts circulation. You next reach the point where your foot begins to curve upward to the ankle. Most hiking boots transition at this point from closed eyelets to open, “quick-lace” hooks. At this point, instead of continuing to lace the boots in the usual criss-cross pattern, instead run each lace straight up to the next quick-lace hooks—you’re basically skipping one lacing criss-cross. (As the video demonstrates, tying a surgeon’s knot—essentially a double-overhand knot—below this point helps keep the appropriate tension over the instep.)
Now take one lace and thread it underneath the opposite lace, between the two adjacent hooks (or hook and eyelet) that the lace is connecting. Do the same with the other lace. Now pull upwards on both laces to tension them down; you’re basically leveraging them off each other for a super-snug and secure fit. If you have additional eyelets above this point, criss-cross your laces normally, and then tie them off with a double knot.
The goal is to apply pressure over your foot where it curves upward, which most directly locks your heel into place (and helps prevent your foot from sliding forward and smashing your toes). You can also apply nearly unlimited pressure here without compromising circulation or causing pain. (In the video, the heel lock is employed higher up, around the ankle, which is not as effective and can also potentially restrict circulation.)