Trying to work out where a 'spare' part goes on Wall-E (21303) I've built a wall-e (set number 21303). This is the corrected version - and I've found, in addition to the 'obvious' spares, like 1x1 flats and round antennae, I have a 4x4 dark grey (4243831) left over. I can't work out where it goes 



Image taken from google images, but its the same part 

The only place where I can find one in the instructions in in step 65/page 54, and the parts count in instructions confirm there are two. The set's built and I don't notice any cosmetic or structural deficiencies in the design, but its bothering me

I've checked through the instruction manual a few times, focusing on the main body (since the arms, and head is paired parts, and there's no space on the neck for a 4x4)

What am I missing?
One is used in step 54 on page 49 and another one in step 65 on page 58. It's likely you missed the one from step 65 as it is just reinforcing the "flap" on the front of Wall-E - not a structural component.