This is likely an "unvention" as Elizabeth Zimmerman would say:  I know I am not the only knitter who has put an item into an envelope to send to a friend to find that it is just a teeny bit too thick to fit through the slot in the guide  at the post office which designates it as a letter and thus requires just over a dollar postage, just that teeny bit too thick which means it shoots into the 'small package' category and the postage would be a bit ridiculous.   

I brought the envelope back home with the intention of removing the cute little knitted buttons which seemed to be causing the extra thickness.  But – darn, they were so cute and added that little extra which is, well – extra. 
Back went the items into the envelope and it was while I was re-positioning them and pushing here and there that I decided it was the spaces between the items that was the problem, that the air kept swooshing around inside and chubbed up the whole thing. 

That's when the "unvention" occurred:  air in sealed envelope;  knitting needles within reach;  stab poke the pointy needle here and here and here and there;  step firmly on envelope (having the presence of mind to remove shoe first with some idea that should some alert postal person notice the holes and wonder if perchance something that needed to breathe might be inside, the imprint of a shoe would not likely be a good idea); have air all be expelled and not seem to be sucked back in. 

I had planned to simply post the parcel at the post office and not risk the curiosity of the postal people but the thought of having the envelope returned for insufficient postage made me hand it over for the slot test.  I held my breath and the package must have done the same because it slipped through  easily, cute buttons included.  Whew!

Here's what was inside – the pocket book slippers, on their way to a friend in Ontario.  The buttons do add that little extra something: I am glad I 'futzed'.