You have rope. You are in a survival situation. One of your first priorities is shelter. Lashing is the skill of using rope with timber to make useful structures including shelter.
First, there are 3 styles of lashing that can really be fundamental techniques.
Square – used for poles at right angles of each other
Diagonal - for poles at angles that tend to fall away from each other
Continuous – for making tables, beds, and other flat surfaces.
Once know you how to build, there are a few options you have for shelter.
Lean-to (1 person)
A lean-to is the simplest and most basic shelter. This is best suited for sun, wind, and rain protection, though generally doesn’t do much for warmth.
2-3 Person Lean-to
The biggest different between this and a standard lean to is that the roof is elongated to allow both people to sleep under it. The additional length can slow rain runoff. However, the benefit of bunking two people together means that one’s body heat helps to warm the other.
Debris Hut / Diamond Wedge
A better choice for the solo person than the lean-to. When used with proper insulation is very effective against the cold. Now proper insulation, does mean that it may feel like a tight fit, but the purpose of a shelter is to contain your body heat
The Watchmen’s hut is best for a group of 2-3 people who have a reason to keep a watch. Reasons could include keeping a fire going through cold night, keeping a lookout for rescue, dangerous predators, or keeping an eye on an injured partner. The benefit is that it has space for two people lying and one to be sitting keeping the watch. Again with everyone in the shelter you share each other’s body heat. If you don’t have a 3rd person but still want to keep watch, you have plenty of room to shelter firewood.