The drawstring bag I was using to hold my gear would get smelly after a while. I wanted a bag that would let my gym accessories breathe. I selected Nylon thread because it is sturdier than regular yarn.

If you enjoy this instructables, please don't forget to vote.
Also, let me know if I need to draw any diagrams to explain the stitches.

If you are unfamiliar with creating double crochet stitches, etc., then refer to the basic crochet information found on various websites and YouTube videos. One good source is
http://www.crochetpatterncentral.com/directory/written_stitch_tutorials.php

Terminology:
CH - chain
DC - double crochet
SC - single crochet
YO - yarn over
ST - stitch

Step 1: Materials

Material:
1. Size I crochet hook
2. Size 8 double pointed needles
3. Hilos La Espiga 100% Nylon No. 6
http://www.creativeyarnsource.com/la_espiga_no_6.html
Price: $6.30
Approximately 1 skein is required. I had some yarn left over when I was finished.
NOTE: However, for an optional bottom pocket, part of another skein may be required.
4. 10 inch Plastic Canvas Circular Sheet Purchased from Joann's.
Price: $2
5. Scrap Fabric
6. Blunt yarn sewing needle
7. Short all-purpose zipper (optional for bottom pocket).

Step 2: Bag Bottom

With size I crochet hook, crochet the following in the round (do not turn):

1: CH 6.

2: Insert hook into the first chain to form a ring. YO and draw the yarn through the stitch and through the loop on the hook to close the loop.

3: CH 3. The CH 3 is considered the first DC stitch. Crochet 11 DC in center of ring
Slip stitch into the upper chain of the first chain 3 stitch to complete.

4: CH 3. 1 DC in the same ST as the CH 3 ST. This is considered 2 DC in 1st stitch.
In the next stitch, crochet 2 DC in the same ST. Crochet 2 DC in each of the stitches around. (24 DC total including the CH 3).
Slip stitch into the upper chain of the first chain 3 stitch.

5: CH 3. 1 DC in the same stitch as the CH 3 stitch. This is considered 2 DC in the first stitch of the round.
*1 DC in the next ST. 2 DC in the next ST.** Repeat from * to **.    (36 DC total)

For each subsequent rows below (6-14) :
At the Beginning of each Row:   CH3 at the beginning and crochet 1 DC in the same stitch as the CH 3 stitch. This is considered 2 DC in the first stitch of the round.

$$In the Middle of each Row:   Add 1 additional DC before the 2 DC ST with each new row.
This is represented by *(1 DC in next ST) X n.
Example: (1 DC in next ST) X 3 indicates 1 DC in each ST 3 times before the next 2 DC.

Repeat from * to ** until end of stitches.
(See Middle of Row Stitches instructions below).

At the End of each Row:   At the end of every row, slip stitch into the upper chain of the first chain 3 stitch.

$$Middle of Row Stitches:

6: *(1 DC in next ST) X 2. 2 DC in the next ST**. (48 DC total)

7: *(1 DC in next ST) X 3. 2 DC in next ST**. (60 DC total)

8: *(1 DC in next ST) X 4. 2 DC in next ST**. (72 DC total)

9: *(1 DC in next ST) X 5. 2 DC in next ST**. (84 DC total)

10: *(1 DC in next ST) X 6. 2 DC in next ST**. (96 DC total)

11: *(1 DC in next ST) X 7. 2 DC in next ST**. (108 DC total)

12: *(1 DC in next ST) X 8. 2 DC in next ST**. (120 DC total)

13: *(1 DC in next ST) X 9. 2 DC in next ST**. (132 DC total)

14: *(1 DC in next ST) X 10. 2 DC in next ST**. (144 DC total)

End of bag bottom

Step 3: Begin the Sides of the Bag

1: CH 3. Working through the front loops only (and not through both loops), crochet 1 DC in each ST around. (144 DC total). Slip stitch to upper chain of the chain 3 stitch. Do not turn.

2 - 8: CH3. Working through both loops as normal, crochet 1 DC in each ST around. (144 DC total).
Repeat row 2 approximately 7 more times. Slip stitch to upper chain of the chain 3 stitch. Do not turn. Work in the round.

9: CH 1. 1 SC in each stitch around. Slip stitch to first SC. Do not turn. Work in the round.

Step 4: Solomon's Knot for Main Sides of the Bag

If the instructions below are not clear on how to create a Solomon's Knot, then search for the many tutorials available on YouTube. Just search for "how to crochet Solomon's Knot".

Terminology:
ESK - edge Solomon's knot. ESKs are shorter than the MSK. Mine was approximately 3/4 inch long.

MSK - main Solomon's knot. Mine was approximately 1 1/4 inch long.

Basically draw a loop of the desired length, yarn over (yo) and draw a loop on the hook. This creates a single back strand.

Keeping the single back strand separate from the 2 front strands, insert the hook under the single back thread (in between the single thread and the double thread), yo and draw a loop through, yo and draw a loop through both loops on the hook. This creates 1 Solomon's knot.

Refer to the stitch diagram for reference for the next few rows.

I marked my size I crochet hook for both sizes (ESK and MSK) to make it easier to measure. Every stitch does not have to be exactly the size. After a while, I just estimated my stitch length.

The following stitches are not worked in the round. At the end of the row, turn and work in the other direction. The seams will be sewed later.

R1: The first row will be created from ESK's only. In the first SC of the row, crochet 1 ESK. Skip 3 stitches and SC in the 4th stitch. *Crochet 1 ESK, skip 3 stitches, and 1 SC in the fourth stitch**. Repeat from * to ** around and end with 1 SC in last stitch.

R2: 1 ESK, 1 MSK, 1 SC in the SC of the previous row. *Crochet 2 MSK, skip next SC, and SC in the next SC of the previous row**. Repeat from * to ** around, and end with 1 SC in last stitch. Turn.

R3 - ?: 2 ESK, 1MSK, 1 SC in the SC of the previous row. *Crochet 2 MSK, skip 1 SC and SC in the next SC of the previous row**. Repeat from * to ** around, and end with 1 SC in last stitch. Turn.

Repeat for the desired number of rows. I created 7 rows total of the Solomon's knot. I checked the size against my boxing glove.

I used safety pins at the end of each ESK to connect the edges to be stitched together later.

R8?: Edge row. 2 ESK, 1SC in the next SC. 2 ESK, skip 1 SC, and SC in the next SC of the previous row**. Repeat around and end with 1 SC.

Step 5: Top of Bag

R1: CH 1. SC in first stitch. 4 SC in the first ESK stitch. *7 SC in the next long 2 ESK stitch (refer to diagram if clarification is needed). 1 SC in the next SC.** Repeat from * to ** around. Do not turn. Work in the round.

R2-R9: SC in each stitch around. Do not turn. Work in the round.
Repeat for about more 8 rows.

R10 - CH 3 in the first stitch. 1 DC in next 2 SC, chain 2, skip next 2 SC, 1DB in the next 3 SC.
(basic pattern is 3 DC followed by CH 2 space). Join to upper chain of CH 3. Do not turn.
This row will be used to thread the straps through.

R11 - CH 1. 1 SC in the next 2 DC, 2 SC in the chain 2 space. * 1 SC in the next 3 DC, 2 SC in the chain 2 space.** Repeat from * to ** around. Do not turn. Work in the rounds.

R12-15 SC in each SC around. Do not turn. Work in the round.
Repeat for 3 more rows and finish off. Cut the yarn. Knot the stitch so that it doesn't unravel.

Step 6: Straps

Using size 8 double pointed needles, knit an I-cord.
If the instructions below are not clear, then refer to the tutorials on the web. Search for 'how to knit an I-cord'.

Cast on 6 stitches. Knit to the end of the row.

Do not turn - instead, slide the stitches to the other side of the needle.

Knit the next row by bringing the yarn behind the work and knit the first stitch. Pull the yarn fairly tight to close the gap.

Repeat this knitting and sliding the stitch until desired length for the strap.

Finish off the end of the strap but do not cut.

Step 7: Finish Off the Bag

Add straps to the top of the bag. Starting at the hole by the seam edge of the Solomon's Knot, weave the I-cord strap in and out of the holes. End with strap going out of the last hole by the edge seam.

R1: Connect the ends of the straps together. Pull the straps evenly. Holding the strap ends together, insert the crochet hook through both of the first loop. YO and draw a loop through the hook. SC in the first stitch.
Insert the hook through the next loops (both strap loops) and SC. Repeat until 5 SC are created that joins the edges of the 2 strap ends. CH 1 and turn.

R2: SC across each SC. Turn

Repeat R2 for about 1 inch.

Finish off. Knot end but leave a long tail to be used for attaching straps to bottom of the bag, as well as to stitch the side seams. Nylon yarn easily unravels so it's better to create as few cut ends as possible. For this reason, I used a long tail from the strap to complete the seams for the bag.

Attach the straps with a slip stitch to the bottom of the bag on either side of the open seam (attached to the row that was worked with only the front loops). Slip stitch for total of 5 stitches to attach to the bag.

Finish off by knotting the end. Thread the yarn through a blunt yarn needle. Weave the tail upwards from the bottom of the bag until the open seams is reached.

Close the side seams with whip stitches. Finish off and knot the end.

I burned the ends of the nylon yarn with a lighter so that it would not unravel.

Step 8: Create Reinforcement for the Bottom of the Bag

I found a round plastic canvas that was just the right size for the bottom of the bag at Joann’s.
The plastic canvas was about 10 inches in diameter.

Fold over a scrap piece of fabric (inside out) to fit the size of the round plastic canvas. Leaving about 1/2 inch from the plastic canvas, sew the seam around but leave a large enough opening so that the canvas can be slipped through.

Turn the fabric outside in.

Slip the plastic canvas inside and fold over and sew up the seams.

Done!

Step 9: Optional Bottom Pocket

If you want to add a zippered bottom pocket for securing keys and wallet, then additional Nylon yarn is required.

Follow instructions for the 'Bag Bottom; and 'Begin the Sides of the Bag. Except for the 'Begin the Sides of the Bag', only crochet about 3 rows instead of 8.

Finish off. Cut long tail. Attach the piece to the bottom of the bag. Whip stitch to the bottom around but leave an opening for the zipper.

Sew the zipper in place.