See for example: http://www.millisecond.com/forums/Topic2274.aspx#2274.
Generally see http://www.millisecond.com/support/docs/v3/html/howto/howtoerase.htm. Specifically, your description seems to imply that your mask is either too small or not positioned correctly.
Regards,
~Dave
hi
i have a problem with setting up primes for the LDT task. i have three different primes that i want to set up and i wanted each prime to be paired with each word one time
i also need to put up a mask so the prime is erased once the word comes up. sometimes i can still see the prime word left up when the other word comes up. i've used the erase element before, but i can't seem to set up the mask.