A stable curtain rod is all you need to add some wonderful window treatments to your home, but if you're a renter, you might not have the option of adding something that essentially punches holes in the wall. Options for renters who can't leave marks on the wall do exist, mainly very strong but removable adhesive hooks, and tension rods that fit inside the window frame. Tension rods are easy to find and come in single and double rod models (for windows where you want both curtains and a sheer liner), but are they the best option?
They Likely Won't Fall Down
One advantage a properly installed tension rod has is that it likely won't fall down. An adhesive hook can lose its adhesive strength over time, and a curtain that is right at the upper limit of the weight that the hooks can hold can pull the rod down suddenly. A tension rod that is the correct size will be wedged between the two inner sides of the window frame or wall area. Unless the curtains are astoundingly heavy and placed on a thin rod, that rod likely is going to stay there until you take it down on purpose.
They Can Be Hard to Install
Tension rods can be difficult to install because some of the longer ones are not the regular "push one end in" type of tension rod. Longer ones often have two pieces connected with a screw that holds the spring in place. These can be difficult to install if you're doing it by yourself. Especially with a heavy curtain sitting on the rod as you try to hold the rod and curtain up while dealing with the screw. If you want to use a tension rod to hold a window treatment, have a friend help you.
They Might Mark the Window Frame After a Long Time
If you leave the tension rod up for years, the ends could make marks on the wall/window frame just from pressure, as well as from dust accumulating on top of the rod end by the wall. You may want to take the rod down periodically to ensure it's not marking up the wall. Adhesive hooks, if you buy the removable kind, shouldn't leave a mark, but again, you might have to install new hooks every couple of years to ensure the adhesive doesn't suddenly fail.
Tension rods can be very handy if you don't want to deal with adhesive hooks. Just be sure to consult a company like Snyders Shades & Shutters to help you with the longer rods and that you check the rod every year or so to avoid dust accumulation that stains the wall.