Step 12Reinforce the seam.
iImage Information

Reinforcing the seams is extremely important in keeping the inflatable heart from popping. The best way to reinforce the seam is to fold it over on top of itself and then fold that over once more (see secondary diagram courtesy of my friend Winnie). Once it is folded three times, sew the seam down once more. With your machine, sew it very slowly and carefully along each seam being mindful not to break the needle as it will be going through thick fabric.