How To Remove Line/Box Around Menu Button on Cellular Phone Vertical Display

How do I display my website on a cellular device(Vertical) without the box/lines around the menu button? See URL: https://www.3tmi.org/

Hi WraysConsultingLLC,
You can use the following CSS code:

@media (max-width: 480px) {
div#gkMobileMenu {
    border-left: 0;
}
}

You ROCK, thank you.