Talking Sign!

Rename the sign to something appropriate for your memory ability.

Make the sign 'Useable', but no inventory. I also made mine 'Plot' but do not know if that had any bearing on the script working.

Create the conversation file. Nothing fancy, do not need to use the wizard or place any calls on the file, but make it a one line without a response call.

At the OnUse script call of the sign, create a new script, named something similar but not identical to the conversation file, and enter the text below for the script.

void main()
{
ActionStartConversation(OBJECT_SELF);
}

The text will appear above the sign as:

Sign:WIPE YOUR FEET!

(Well, that's what MINE says)