drop across someone or something
[for something long or wide] to fall on and lay on someone or something. A snake dropped across the hood of the tourist bus as it passed under a tree. As I lay sleeping, a ceiling panel dropped across me and woke me up.
drop something across something
to let something fall in such a way that a span is bridged; to let something fall in such a way that a pathway is blocked. Let's drop a little rug across the threshold. They dropped a huge boulder across the road so no one could pass.