You can join two lines together using the sheet bend knot. It is easy and quick to tie making it one of the most useful knots to learn.
You can also use this knot to connect a line to a corner of a tarp or poncho. As a result this can be very useful when making a simple lean-to shelter. This gives the sheet bend knot another useful function for the backpacker.
You can easily make the knot more secure. You do this by making another pass with the line as illustrated. The double loop reduces the chances of the knot folding and coming lose.
Securing two lines together
This knot can be quickly tied as illustrated in the diagram to the right. The final and important step is to tighten the knot. A lose sheet bend knot can slip.
You should always verify that the two free ends are on the same side of the knot as illustrated in the diagram. If the free ends are on opposite sides you tied the knot incorrectly and it will slip.

Note: The two free ends are on the same side. If the two free ends are not on the same side the knot will quickly slip.
Secure a line to a tarp or poncho corner
The sheet bend knot can be quickly tied to a corner of a poncho or tarp as illustrated in the diagram to the right. The final and important step is to tighten the knot. A lose sheet bend knot can slip.
You should always verify that the two free ends are on the same side of the knot as illustrated in the diagram. If the free ends are on opposite sides you tied the knot incorrectly and it will slip.

Note: By twisting the corner of the poncho or tarp you make it act like a line.
Bonus: Double Sheet Bend

To make a more secure knot you can quickly convert the knot to a double sheet bend knot. In order to make a double sheet bend make another loop around as illustrated above. Because of the extra loop the knot is less likely to buckle and come undone. Always verify that the two free ends of the line are on the same side of the knot.