Answer:
What word has kst in the middle, in the beginning, and at the end?
Keep doing me to avoid lens dryness
I live off of a busy street. If you want, you can stay for an hour or two. But if you don't pay rent, I'll tell on you. What am I?
What has many keys but can't open a single lock?
Send poorly behaved children to me and let them sit here.
Whoever made me don't want me. Whoever bought me don't need me. Whoever use me don't know me.