I wasn't satisfied with existing answers, so I had to do some research of my own.
If you know a good knot and technique for this case, please post an answer and earn your upvotes!!
Do not use these for critical loads! Do not put your life on knots without securing the ends from slipping!
If you can overtighten: the sheet bend (aka weaver's bend)
I came ...
You need to be looking for semi-static rope, as used by cavers for SRT, usually of thickness between 8.5 and 11.0 mm. It's normally sold in 200-metre reels, though most retailers will cut to a specific length for you.
The only difference to caving rope is that some specialist canyon ropes are designed to be less dense than water, so they float rather than ...
My favourite knot would be the taut-line hitch. While it is usually tied to form an adjustable loop, it can be used to connect two different ropes. It has the benefit that it can be tied rather easily with some slack and then adjusted for the required tension with both hands.
In the pictures below it is used to tie a loop, but it works the same way to ...
All of these require slack. If you need to tension the system to bring the ends together, find a longer piece of rope, the one you're using is too short.
Reef (Square) knot
Easily tied, everyone knows it, the only problem is that tying it under tension requires 3 hands.
Sheet bend (because you've mentioned it)
Not really designed for tying under tension, ...
Some manufacturers state that soft goods such as ropes and dogbones can be damaged by markers so it is best practice not to mark them with sharpies or other generic markers. If you do wish to mark them, there are special markers designed for the purpose. For example, see this one by Beal.
It's possible that it could damage the soft gear,
Tests done by the UIAA Safety Commission and some rope manufacturers have shown that marking
ropes with liquids such as those provided by felt-tipped pens can damage them; even with those
markers, sold specifically for marking ropes. The test results have shown a decrease of up to 50% of the
(Maybe not a great answer, but too long for a comment.) I guess this would all depend on how much tension we're talking and how much extra line you'll have (and whether you have another set of hands). When I'm trussing a roast, I use a surgeon's knot to help maintain a small amount of tension while I finish the knot. You use the multiple wraps to build in ...