Move to first character on the command line

I am using CSH inside SCREEN on a PUTTY terminal. When I have to repeatedly enter similar commands, I tend to press the up arrow or use the shell history to bring up the command at the prompt. However I realise that there is a switch right at the beginning of the command that I need to change.

How do I quickly move to the first character of the command

Nope!!! <HOME> does not work for me.

Instead I press Ctrl + x twice to toggle cursor position from the first character to the last character of the command.

I do not know if this shortcut is provide by CSH or by Screen or by Putty, but it does work for me right now.

Move to first character on the command line