I came up with a simple solution...
Create a new image. I used Microsoft paint.
Set it's width to 1000.
Use the fill-in to make it all black.
Set the height to 1.
Save it.
Upload it in the Meme Generator. Be sure to name it (I used "single black line") and check to allow other users to use it (they won't be able to, but that's how it gets added to your My Templates tab).
On My Templates, it shows as a black square.
You can then hit Add Image and search for any image on Imgflip, or upload an image you don't want to have to add to your My Templates.
Be sure you put the added image below or it will vanish.
The line won't show if the image's width is 500 or less.
It's just a handy tool...
Caption this Meme
