Weaving with a temple is not for straight selvedges but for keeping the outer warp threads from breaking due to rubbing on the reed caused by draw-in. Some experts recommend that you never weave without one. Using a temple has greatly improved my weaving.
If you don't have a temple or the cash for a fancy one, you can easily improvise one with inexpensive materials.
If your loom doesn't have side supports, attach a curtain rod to the side of your loom.
Take a couple of, 1lb bags of dried beans (found at the grocery store) or rice and cover them with cloth. Bend a paper clip to make a hook on the bags. Then tie some string to the "hook". Attack tarp clamps or suspender clips to the other end. You can find tar[ clamps in the hardware store in the rope and tarp section. Sturdy suspender clips can be reclaimed off used suspenders from the thrift store. I like the suspender clips the best as I found trying to unlock the tarp clamps hurt my arthritic hands. The suspender clips are easier to work.