Inside the Insight voting machine that people in the US must have used on Nov 8 to insert their filled out ballots,, there are actually two white bins that collect the ballots, one smaller than the other. Why are there two instead of one big bin?
One bin is used for write-in votes, while the other is used for ballots without write-ins. This allows the pollworkers to more easily find the ballots they need to manually process.
There is also a third bin, but it's inaccessible unless the pollworkers unlock it. This is used if the machine is malfunctioning, and ballots are just put in there manually.
From Verified Voting (emphasis mine):
The voter inserts the ballot into the scanner at the top of the device, which reads the marks on the ballot. If the voter has overvoted (voted for more candidates than eligible), the Insight will eject the ballot for the voter to review again, or deposit the ballot into the ballot box. If the voter has cast a write-in vote, the scanner will feed the ballot into a center bin so that pollworkers may process the write-in votes. Ballots that require no review by pollworkers are deposited into a rear bin. A front, auxiliary bin is available in case the machine is not functioning during polling hours; voters deposit ballots into the auxilary bin manually, but they will not be able to use the auxilary bin unless pollworkers have unlocked it.