You can not get by in construction without a leather tool bag. I learned this way back when I worked framing houses in the hot Texas summer. From my first day on the job I learned the importance of a good leather tool bag.
A lot of people do not know this but when searching around for the best leather tool bag to use you need to know that the tool bag is the pouch that is worn on the right side of your body. In construction we generally referred to both of the bags worn around a leather or webbed belt as tool bags but for specific sake the one on the right is the tool bag. Now this assumes that you are right handed. If you are left handed you would probably wear your leather tool bag on the left side. It is the tool pouch that has the hole for holding a hammer and other tools. The one worn on the other side is called a specialty tool bag. Pretty much the same thing but you will need both to have a full set of tool pouches.
Regardless when looking for a leather tool bag be sure to choose one that has a few key characteristics. For one you will need for it to be made of leather since the nylon tool bags will not hold up as long. I have seen guys use the leather tool bags for as long as thirty years. That is a long time but the leather can hold up to it because it is tough.
Another thing to consider is size. You want to strike a balance between being big enough to carry all of your tools but not so big that it is weighing you down. You can find a few different sizes and these usually mean that they just have different spaces for different tools. You will need different tools depending on what kind of job you work on.
But do not think that a good leather tool bag is only for those in the construction field. I have found that having a good quality leather tool bag is a great thing around the house. Just doing every day handyman jobs on my home it is nice to have a good pouch to hold the things I am using on the job I am working on. How many times have you been on a ladder just to have to climb down and grab a hammer or nails or something? And also there are the times that you set your tools down on the ladder only to have them fall off. With a good tool bag those problems are a thing of the past.