I have some wool clothes that I lengthened by taking out the hem and resewing it with a smaller hem. Now I have crease marks from where the hem was folded before. How do I remove the fold line? Is there a method that will loosen the weave of the fabric, just enough to iron it out without damaging it?
If you can wash the item (read the instructions on the label) that can be done before you steam. Washing will get the fabric to relax but many wool items of clothing can not be washed or only very carefully.
If you can not wash or do not want to try, you should start with steaming, just steam for now, no ironing at the moment.
Best start with hanging it in the bathroom while you have a shower. Not in the water but where it will get the warm mist.
If that is not enough try holding it for a while over water that is hot enough for steam but is not on a stove still.
Look what the results are before you try the next step, if you can safely do so, you can hold it over the steam coming from a kettle on the fire, but be careful, fire and hot water can both give nasty burns.
After steam, ironing under a wet cloth might be the best next step.
This cloth should be wet but just not dripping, cotton is traditionally used. My mother used an old white cotton tea towel for this.
Using a steam iron might work as well, but it is more suitable for cottons than for serious work on wool. (As wool should not be ironed that hot.)