tie up

verb

To secure with rope, string, etc.
“Don't forget to tie up your hair before you bake.”
“The robbers tied up the bank employees before forcing a way into the vault.”
To occupy, detain, keep busy, or delay.
“He has been tying up the phone lines for hours now.”
“Just how much traffic was tied up was not immediately determined but in Houston about 150 cars of grain arrived yesterday and could not be transferred to the port because of the Port Terminal Railroad picketing.”
To complete, finish, or resolve.
“I'd like to tie up the project before I leave.”
“Scottish Fishermen’s Federation chief Elspeth Macdonald said the whitefish fleet could have had to tie up for the entire year because of the recommendation.”
To immobilize a capital: make a capital investment that makes that capital unavailable.
“Don't tie up your capital in aging accounts.”