Clever... I use 'supermagnets' like those for all kinds of things besides holding picture on my refrigerator's door.

But I have to ask: what purpose does the steel your magnets are attracted to serve during a peapod's build?

I'd be one to swap pushpins for thumbtacks were I building a 'pod; heads're bigger, shanks're longer, points usually 'pointier' so what holes you make are smaller than those from thumbtacks.

   Boats, paddles, and miscellaneous things I have epoxied fiberglass onto and I have yet to thumbtack, clamp, stitch or otherwise affix the glass to the item. I am courious as to why you'd have to pin it. 

In any event concidering stitch holes and other minor blemishes you would have to look real hard to see them after the glass , epoxy, and varnish(paint).  

   @spclark: I match each magnet inside the hull with one on the outside, there is no piece of steel anywhere. The only purpose is to hold the fiberglass fabric in place while getting it cut to size and shape, and allow me to adjust it easily which is not so easy with pins.

@Grumpy: most likely its just my inexperience, but I'm building this solo and especially the bow and stern are not easy to lay fiber in without it flopping down.

crowcoder thanks for the explanation. Using a magnet on both sides never crossed my mind. Your approach is a very creative means to an end that very likely improves your experience! Thanks for sharing!

   I just hold it in place with masking tape

 "  @Grumpy: most likely its just my inexperience, but I'm building this solo and especially the bow and stern are not easy to lay fiber in without it flopping down....."

Well, yes but all you have to do is a spring clamp at the top of the inside, some tape or if its where I think you're talking about just a blob of epoxy.  And likely there's a long tail of cloth hanging over the edge to be trimmed later (or should be).   Its gummy I've often just put a small blob of epoxy under the cloth, in the area to be bonded anyway, to temp hold it as I work from the center to that location.  

   ...... what ever works best for you.