When cutting the rug canvas to your desired size add at least 4 squares onto each side.
A brand new piece of rug canvas will have a thick edge at both the top & bottom which needs to be cut off since you cannot hook through it. The canvas thread from these cut off edges is very strong and is useful in tying down the edges and being used as a needle threader. So pull off a few pieces of this canvas thread.
Count at least 4 squares on each side to fold down and use the canvas thread to tie the edge down. I made ties at every blue line on my canvas or about 10 squares. Most videos or instructions I saw online did not have this step but I found the large canvas easier to handle with the edges secured.
The corners get a little difficult since there are now four layers of the canvas folded there. Do not try to cut parts of it away to make it easier to loop through. Trust me; I tried and it didn't work. Use the wide end of the locker needle to align the holes for tying.
Simply use a doubled up length of your yarn with a tapestry needle to whip-stitch all the edges of the canvas. The yarn I used is quite thick and difficult to get into a tapestry needle. The canvas thread is strong enough to be used as a needle threader for this yarn. Do not make any knots or tie the yarn to the canvas. Leave long tails which can be tucked into the finished stitches. This creates a nice smooth finish.
I initially whip-stitched the edges once with the doubled-up yarn and when I finished I decided to make the edges a bit thicker to make it more defined, so I whip-stitched a second time with another doubled-up length of yarn. So, my end product has four strands of yarn on the edges.
Here is a short video showing just a few whip stitches and how to tuck the tails into the finished stitches.
Thread a doubled-up arm's length of yarn through the eye of the locker hook. This is now the "locking medium." Many instructions online say to use cotton twine or an inexpensive yarn as the locking medium. I choose to use a doubled-up length of the rug yarn so it would be thick and soft to walk on, and when it comes time to tuck in all the tail pieces it is easier to hide them in the loops of the rug.
The yarn I chose for this project is a multi-colored gradient blend. So I used separate skeins of yarn for my locking medium and pulled the loops constantly from one skein. You can pull loops until the skein is completely used without having to cut the yarn at all. This cuts down the number of tails to be tucked in at the end, and with a gradient blend the striping comes out nice and smooth. (See the final pictures)
It is best to use only an arm's length of yarn for the the locking medium because (1) it is faster and easier to pull lots of smaller lengths and (2) the yarn tends to get pulled and "pilled" up if it is too long and pulled through too many loops.
I suggest varying the lengths of yarn for the locking medium by a few inches so the end tails do not all fall within a straight line on your rug. If they do, it may tend to make the rug look like there is a road bump running down where all the tails are tucked in. I used a heavily textured yarn, which also helps to hide the tails, and it gives the rug more of a bouclé texture.
Insert the hook into the next hole and hook the rug yarn and pull back through. Keep the yarn on the needle shaft and make the loop about 1/4". Then inset the hook into the next hole and hook the rug yarn again and pull another loop up through and onto the needle shaft.
Once you have a few loops onto your needle pull the locking medium through the loops while holding onto the tails of the locking yarn. Now you will have 3 tails at the same place to be tucked in later. Always hold these tails when pulling the needle so you don't pull the locking yarn all the way out of the loops.
Depending on the thickness of the material you chose for your rug, you can hook anywhere from 4 to 8 loops onto the locker hook needle before pulling the locking medium through. When you reach the end of the row, rotate your canvas around and continue hooking loops on the next row.
The corners where four layers of canvas overlapped is not too difficult but it was tight so I worked it 2 loops at a time.
When you reach the end of your locking medium leave enough of a tail to be tucked in later.
After the canvas has been completely hooked go back and tuck all the tails in. Tuck all the tails into the loops on the top of the rug. This keeps the underside of the rug nice and smooth (if the rug is to be used on a wood or tile floor add rug backing for safety).
Many instructions online use the locker hook needle to tuck the tails in but I think it is too thick and may pull your loops askew. I recommend using the tapestry needle. Pull the tails into rows next to them in the opposite direction from the way the rest of the locking medium was being pulled. Snip off any excess tails that haven't been tucked in.
Tip: The rug I made was 57" long and the canvas was stiff and difficult to work with (at first). I rolled up the ends of the canvas and used a few jumbo binder clips to hold the rolls so I had a smaller area to work with and I could hold it all in my lap while hooking.
In the underside picture you can see that all the edges and knots that tie the edges are barely visible and the back is smooth and can have rubber backing easily added to it.
It took me 5 days (& lots of movie watching) to make this 57"x21" rug for my guest room.