Putting horizontal lines on two images placed side by side after every 20 pixels heightwise.

Hello, I have two images and I want to put those two images side by side and then want to draw horizontal lines on those images in a gap of every 20 pixels heightwise. For example if height is 480 pixels then number of lines will be 480/20 = 24. All 24 lines at equal distance of 20 pixels on both images. Following figure shows the demo what I want.

I did this in Python but want to do same in Matlab. Also, I don't want to change images sizes. I know I can used

imshowpair(J1, J2, 'montage')

but I am not able to draw horizontal lines on this montage. My images are :

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