I was changing out the keyboad on a 2008 Aluminum Uni-body Macbook. The whole keyboard had be spoiled by a spill.
The replacement that I got didn't include the trackpad so I had to swap this out from the broken one. The Y bits were needed for this and it turned out neither of the one's in the kit would fit the little tensioning slug at the bottom of the trackpad because they were both too pointy. I noticed that the driver they were using in the iFixit instructions wasn't he one from the kit. The one's in the kit are too pointy to fit that slug.
Got it out easily but getting it in mostly involved a munged up plastic spudger (or black stick as Apple calls it) and a pair of needle nosed plyers. The bits in the kit would have to be ground almost flat an the tip to fit the slot.