In preparing my hackerspace friends, for our Late arriving (due to shipping snafu) October buildnight dodocase Virtual reality headsets for smartphones. I started dabbling with lasercutting my own, and looking at how to attach a headstrap. because while holding it to your face works for a lot of the things, its both tiring, and some apps need a game controller or other input and its nice to just be able to use your head.

I tried a few things, but finally decided snaps worked pretty well.

you will need,

a google cardboard vr viewer
some 3/16" steel snaps
a snap setter pliers (or they make a tool to let you use a hammer too, pliers like above pictured available on Amazon worked great)
some elastic banding i used 1/2" wide, but you can use anything wide enough for the snaps

Step 1: Step 1

Make sure the cardboard is fully assembled. and the way you like it. you probably won't be able to unfold it again after these mods.

There are 3 parts to these 3/16" steel snaps, there are male (nubby) snap parts, and female (the one with the hole in it) and then there are rings with points. the rings are used on the back side of both the Male and Female snap parts.

Get out 2 pointy rings, and 1 male, and 1 female snap.

Step 2: Lets Get Snappy

Locate somewhere on the temple sides (i centered mine along the edge that runs from your cheek to your temple)

Take the pointy ring and press the pointy side into the cardboard from the inside of the goggles. you should just barely see the points sticking out.

Select the female snap parts and place it on the points, (the correct side will be the side with a slight folded lip around the outside (where the points are going to curl into) its more obvious on the male snap parts so compare them)

Crimp down pretty hard with your pliers, making sure they are well centered in the snap pliers. release and look to make sure the points all went inside the snap ring. and are not poking out and that the snap is now affixed well.

Repeat for the other side, and if you want a nice support sling over the top, put one in the middle of the velcro flap that holds your phone in, i put all female snaps on the cardboard, and male on the straps, makes it easier to swap and try other configs.

Step 3: Strapping Young Lad/lass

Now at one end of the elastic follow the previous steps to set a snap (male type) and go ahead and snap it in place.

Then hold the cardboard to your face and see how much elastic you need to be snug but not digging the cardboard into your face.

Mark that spot and put in another snap. (be smarter than me, and get the snaps all facing the same way (you can see in my 34d photo the left side has one nsap facing outwards. I left it there for future attachment or other options. but I may cut it off sometime. )

try it out, if multiple people are going to use the cardboard, you might even putin several snaps to allow for adjustment.

then cut off the remaining elastic.

Step 4: Over the Top Strap

Heavy cellphones can make the google cardboard kind of sag or tilt down your face, adding a snap to the top of the cardboard, and to the middle of the back of the headstrap, you can now make an optional over the head strap.

once again set one male snap, in the end of your remaining elastic, and snap it to the goggles. then wear and test where the strap meets the back snap with just a teeny bit of tension.

set the 2nd snap, and then cut off any additional elastic.

-Fin!

I have collected other bits of cardboard links and tips. feel free to snag any that you like.
http://tinyurl.com/adricscardboard