So you have made a bag, now what should you use for a drawstring? You can really use just about anything, but some things are truly better than others. What you select frequently is just a matter of what you have on hand, but there are many things you can and should consider.
First, how big is the opening for inserting the drawstring? How big is the overall casing? Are you using a drawstring tool or a safety pin? What size? Make sure both the tool and the drawstring are not too big for the opening!
Most of my bags have a 1/2" to 3/4" casing, and the openings are all 1/2" or larger. This means that the ideal size drawstring is less than 1/2", so I can use any drawstring up to 3/8" wide. Pictured above are a variety of types of drawstring varying from braided cords, shoelaces, twisted cottons and ribbons. I did not include elastic or any other materials that stretch since they don't work well.
I prefer to use the rounded cords, but I'm not a fan of either the braided or twisted cords shown above. It is difficult to get a good tight knot on the ends of the braided cords - especially the heavy ones such as parachute cord. Yes, you could solve this using a cord lock, but if you are using the bag for knitting or other fiber crafts then the cord lock can tangle in your yarn! Also, the ends of braided cord will unravel unless you have access to the type of equipment that puts the plastic ends on shoelaces 🙂
The twisted cords knot well and are a good all-purpose cord, but the ends will really fray and the cord will untwist.
I love the smooth gliding action of satin ribbon in my bags and my strong preference is to use Satin Rattail which is available in a variety of thicknesses. Unfortunately some of my customers don't care for it because either the knot has come undone - or their cats like to chew on it! Because rattail is round rather than flat it doesn't twist inside the casing. I've tried the flat satin ribbon as an alternative but in my experience it is a bit limp. Currently I am using grosgrain ribbon for all drawstring top bags. It is a bit sturdier than satin ribbon and bags stay cinched closed. It is easy to knot and if you cut the ends at an angle and melt them a tiny bit they don't fray. The 3/8" width is perfect for most bags, though I will use the 1/4" width on smaller bags.
Oh, and what do I use to insert the drawstring? I use a bodkin. I like to joke that you shouldn't work at a fabric store if you don't know what a bodkin is!