rap at

rap at something

 and rap on something
to tap on something to attract someone's attention. Who is that rapping at my door? Someone is rapping at the window, trying to get my attention. I will rap on her window and try to wake her.
See also: rap
References in periodicals archive ?
Researchers evaluated plant-produced mixtures with high RAP content (25 and 40 percent), different binders (PG64-22 and the softer PG58-28), and a control mixture with no RAP The study improved the understanding of the performance characteristics of hot-mix asphalt (HMA) mixtures with RAP at high, intermediate, and low temperatures and examined plant-produced HMA mixtures containing RAP.
The 28-year-old Science Communication student at the University of Glamorgan has also been asked to perform his rap at the Science Museum in London on Wednesday evening.
Rap at best, she says, is a "petition," a plea from young people to look at their lives.
Will Smith got his start in show business in Philadelphia at the age of 12 when he began to rap at house and block parties.