Leigh asked if I always use a temple in my weaving. The answer is no, I do not. When I am weaving fairly narrow (10-14") and fine (60/2 silk) silk warps, there seems to be no need for a temple. I think that may be due to the fact that I ratchet up the tension on the warp to maximum. Silk is very strong and seems to have had no tendency to break at such high tension. And it is also fairly easy to get the number of picks per inch at those widths.
Also I have not used a temple weaving my own handspun, though again the warps were relatively narrow (15" to 20"). Also, I found I could keep the warp tension quite high. This surprised me as my handspun is quite soft and very stretchy. The first time I made a warp with some, I was amazed at how it snapped back to a much smaller size when I took it off the warping board. Needless to say I made a mental note to calculate for that in planning the next handspun warp! Also, I did not need a temple because I was not packing in the weft tightly, as I do with the fine silk.
When I do use temples should become fairly clear now! I use them on wide warps. The temple keeps the whole warp stretched widthwise so that it is easier to get the number of picks into an inch that I need/want.
One thing a temple does not do is to prevent draw-in. When you remove the temple that fabric is going to draw in. Draw-in is just the nature of the beast. What it does do is to keep the warp stretched at the point of weaving so that you can pack the weft in more easily and to distribute the draw-in a little more evenly across the entire width of the fabric.
The top left picture shows a very small temple from the top side. The top right picture shows its business side. You can see the prongs on the side that is lighted (I do have to work on my photography skills!). The bottom picture shows the temple with the two pieces separated. One part of the temple has a little upright piece that fiats into the holes you see on the other piece. The white band you see in the top two photos then slides across both pieces to hold them in place. A wicked, wicked piece of equipment.
Draw-in is just the nature of the beast. You can, however, weave with virtually no draw-in if you use something like fine fishing line for the selvedge edges and then remove it when you are done. I have done this when weave a blanket in 3 pieces. I put the fishing line on those edges that were going to be joined. I wanted those edges to look just like the rest of the blanket after seaming. And, thanks to fulling, you have to look for those seams to find them.