Black Widow 2021 Harness

Designer: Lauren DeMarti

Instagram: @thecosplayhistorian

YouTube: Lauren - The Cosplay 

Twitter: @sewinglauren 

TikTok: thecosplayhistorian


This tutorial for Black Widow’s harness is the perfect way to finish your movie cosplay! We will be using easy-to-find materials like EVA foam and some crafting tools.


OLFA Tools Needed:


Other Tools and Materials:

  • Black Widow 2021 Black Suit Harness - Foam Pattern & STL
  • 1 sheet of 2mm EVA foam - sold at Joann (Yaya Han line). I also love TNT Cosplay Supplies online.
  • Contact cement (Barge)
  • Heat gun
  • Rotary tool
  • Respirator
  • 1” black elastic
  • 1” black velcro
  • A small-ish piece of thermoplastic or scrap plastic
  • Two 3D-printed “hinges” - or cut these out of EVA foam!
  • Black Plastidip


1. You will need to 3D print two (2) pieces of my “hinge” STL file, or cut a similar shape from EVA foam and round off the edges. You also have the option to not include any hinges - I don’t think it would detract from the overall look of the harness to go without!

2. Using my free pattern and your OLFA Art Knife, cut the pieces below out of 2mm EVA foam:
     a. 2 pieces of Side Straps
     b. 2 pieces of Center Strap
     c. 2 pieces each of Overlay 1, Overlay 2, Overlay 3, and Overlay 4
Be sure to cut on top of your OLFA Cutting Mat!

3. Using a rotary tool, round off all edges of your Overlay pieces.

4. Before gluing any foam together, machine sew a strip of elastic to the underarm edge of you Side Straps. The stitching will later be covered by the Overlay pieces.

5. Apply a thin layer of contact cement to one side of each Side Strap, Center Strap, and all Overlay pieces.
TIP: be sure to wear a respirator while working with contact cement to protect your health.

6. Once 5-20 minutes have passed, place the glued sides of both Center Strap pieces together, and place all Overlay pieces on top of your Side Straps as marked.

7. Using your OLFA Beginner Craft Knife, score one side of your Center Strap piece along marked lines. The Beginner Knife is perfect because you won’t accidentally cut too deep! You do not want to cut all the way through your foam.

8. While wearing your respirator - foam releases toxic fumes when heated! - carefully heat seal all foam pieces. Keep the heat gun a good distance away (~12”) so as not to melt the foam! The foam will look a bit smoother and slightly shiny after.

9. Protecting the elastic with some scrap paper, coat all foam pieces in Plastidip. Let dry between coats - you will need 3-4 coats.

10. Using your OLFA Heavy Duty Snap Off Knife, cut one piece of Backpack Base from scrap plastic and coat with either Plastidip, spray paint, or basic black paint. This heavy-duty blade will cut better through thicker plastic.

11. Use contact cement, or a curved needle and thread, to attach all pieces together. The Center Strap will be nestled between each Side Strap piece. If you choose to use the hinges, it will be Side Strap - Hinge - Center Strap - Hinge - Side Strap

12. IMPORTANT: Leave one connection between Side Strap and Center Strap unglued - this is where you will attach your elastic so that you can get in and out of the harness. Glue or stitch your velcro to the backside of both pieces.

13. Using a dress form or a friend to help you, mark where you shoulder straps and elastic need to meet the Backpack Base. Push some holes into the plastic, and hand sew your straps at the top of the base, and your elastic at the bottom. You may also choose to glue these!

You may also choose to glue a strong black fabric to the backside of your finished foam pieces. This is optional, but it will add some extra strength.

And that’s it! The project may seem overwhelming when looking at the pieces, but it is a lot of repetition of the same type of steps.

You can glue or velcro your backpack of choice on top of the Backpack Base - whether this is made from foam, 3D printed, or is a piece bought from a cosplay company!



Check out this great video tutorial that accompanies the instructions above.

For this and other great video tutorials check out The Cosplay Historian on YouTube.