You have mentioned several locations not just one. Since most of your other queries have to do with Gol or Nes in Buskerud that's where I looked.
The letter u is indicating that 'Glitre' and 'Smeplassen' are small subfarms UNDER Hesla and Rust. Hesla and Rust are names of farms that can be found in Gol, Buskerud. They appear there in the 1801 Norwegian census database.http://home.online.no/~otjoerge/files/word.htm