Motor cars, handle bars,
Bicycles for two.
Broken hearted jubilee.
Parachutes, army boots,
Sleeping bags for two.
Sentimental jamboree.
Buy! buy!
Says the sign in the shop window.
Why? why?
Says the junk in the yard. [ Lyrics from: http://www.lyricsmode.com/lyrics/p/paul_mccartney/junk.html ]
Da da ya da da da,
Da da da,
Da da ya da da,
Da da da da da da da.
Candlesticks, building bricks,
Something old and new.
Memories for you and me.
Buy! buy!
Says the sign in the shop window.
Why? why?
Says the junk in the yard.
This is simply a breakup song. Paul goes over the things shared by the couple (cars, bikes, things that they only would understand the sentimental meaning of) and how they purchased them together ("buy! Buy!... ") and now that they've broken up, they're just junk in the yard, either tossed away, or more likely for sale ("why? Why?... ").