KeyDown - Holding the key

How do I press the backspace button and have it hold for 10 seconds?
Reason is I need to go to a url and remove what’s already on there.

this is not working:
click url
set option keydowndelay, 10
keydown backspace
wait 10
keyup allkeys
setoption keydowndelay, 0

Holding the key down that way doesn’t work because of the way the key repeat works on the SUT. A better way of handling that operation is doing a select all and delete:

click URL
TypeText controlkey, "a"  -- select all
TypeText backspace

perfect, it worked