Bridge the gap is a phrase used figuratively. The same idea results in the term a bridging loan, which is a loan required when one house has not been sold in time to complete the purchase of the next.
A bolt hole is usually somewhere to hide. To bolt means to run away. When nuts and bolts are used a bolt fits in a hole.
A hidey hole is a secret hiding place.
Holey socks are socks with holes in.
A loophole is a way of avoiding some rules and regulations. It is also a piece of hardware – a metal loop with a screw fitting.
To loop the loop is to perform a particular aerobatic feat.
A hole in the wall used to have a literal meaning. In Shakespeare’s play A Midsummer Night’s Dream there is a play within the play. One of the characters is the wall with a hole through which Pyramus and Thisbe talk. Nowadays there is a new meaning – ATMs (Automatic Teller Machines) dispense bank notes through a hole in the wall.
Stone-walling is an expression meaning deliberately working slowly even to the point of being obstructive. Dry stone walls are built slowly with care and skill. They are a feature of the rural landscape in many parts of Britain.
The writing on the wall is not always graffiti! The expression is used about warnings of future disaster. The story in the Bible, which led to this being a popular expression, is about King Nebuchadnezzar. Daniel 5.