What Knot To Use

I would use a clove hitch.

What are they for? Sails, yards?

Personally, I generally use a simple overhand knot unless it is a very large scale model, as in some small ships.

When Mr. Stauffer talks about the overhand knot, I think he's referring to what sailors call the reef knot and Boy Scouts call the square knot.  It's the basic knot that just about everybody knows how to tie.

The truth is that, in ship modeling, there's regular use for only two knots:  the reef/square/overhand knot and the clove hitch.  Both are extremely easy to tie.  The clove hitch only has one frequent use:  for tying ratlines to shrouds.  For virtually every other purpose, the reef/overhand/square knot is fine.  I've occasionally had a use for the bowline (which I have to look up whenever I tie it).  There are literally thousands of knots out there, but for ship modeling you really only need two.

Professor; The rabbit comes out of the hole, around the tree and back into the hole.

You could also seize it, depending on how it needs to be connected, as through an eye bolt etc.

Of course not as fancy as in the above.

But generally, I concurr w/ everyone else. A simple overhand or clove hitch will do.

Yeah, I've heard about that rabbit going around the tree and down the hole for at least forty years - but I use the bowline so seldom that I still have to look it up every time.

Seizing is another way to fasten lines - to themselves or each other.  The question that started this thread had to do with fastening blocks to yards; for that job the good ol' square knot is certainly the appropriate one.  But seizing is almost essential for all sorts of other rigging jobs.

Jackstay, eyebolt, around the yard?

I have the impression that the model in question is the Revell Constitution.  (If I'm wrong, somebody please correct me.)  The kit represents the ship in her 1814 configuration.  That's a bit too early for jackstays; they seem to have been introduced somewhere in the neighborhood of 1820 (or maybe a little earlier).  Prior to the introduction of the jackstay, it was normal to attach blocks directly to the yard. 

Actually, the usual method was to strop the block with a rope in the groove around the block's circumference, turn an eyesplice in each end of the strop, and seize the two eyesplices together around the yard.  But that's pretty finicky for 1/8"=1' scale.

Yes, It is the Constitution. Thank you for your tip. The problem I have is that if you clip the ends close to the knot, the knot unravels. If you leave some line, it looks bad. Is the solution ac dab of CA. Or do you have some other method of taking care of the loose ends?

for going around a yard, I tie on the other way around.  

First, I go around the yard.  If the block needs a bit of strop, like for a clew, I'll seize line around the yard with fine thread.  That gets a tiny dab of CA.  

Put another seizing on the doubled lines the correct distance along.  Then, take the line around the block and tie it off with the remaining line using a simple overhand hitch (half a reef/square knot), with a dab of CA to make that sure.  

If the block is snubbed up close--bunt or naval brace blocks, for instance--then a quick overhand around the yard.  Then snub the block inside another overhand knot secured with CA.

Leave the ends long if this is rigged as a gun tackle; the bitter end of the working line can be knotted right to the end of the block and strop.

Clove hitch is very hand--IMO--at small scale, under 1/72 or so, for tying off the bottom bullseye for stays.  You leave one leg of the hitch very long, roll the "knot" side under.  Use the long leg to make up the lanyard in the bullseye, and it comes back to tie back to itself.

I always use a very tiny dab of CA on knots. That way you can snip really close w/ out it coming undone. A touch of dull coat later will kill the shine from when it dries.  I am building the Connie right now as well. I would really like to see your progress. Thought about posting your build?

There is a superb book by Lennarth Petersson "Rigging Period Ship Models" that is nothing but illustrations of every single line and how it is attached and belayed. Spendy, but very much worth the money.