drawbridge

noun2

1. •
   A hinged bridge which can be raised (to prevent its being crossed, as across a moat, or to allow watercraft to travel beneath it).

   • I might jump an open drawbridge, or Tarzan from a vine / 'Cause I'm the unknown stuntman that makes Eastwood look so fine — 1981
2. •
   [before a noun] (figurative) A tendency to provide only limited access.

   • I looked at her with wide eyes, and the drawbridge of her reserve fell instantly. — 1873