A little light getting in doesn't usually ruin a darkroom. If you are really talking about just a little. I recall a discussion where a photographer thought his attic was dark enough but he would carry the exposed prints across the room from enlarger to trays, and would fog his prints when he walked past the light fixture for the room below, because the can leaked.
Also if the light strikes your eyes, it doesn't necessarily strike the prints. I use black felt curtains to block light out of my darkroom. The other day I was reeling some Plus-X when I noticed one of the curtains wasn't pulled over all the way. I hadn't noticed until my eyes adjusted, then I quickly finished the reel, put it in the tank, closed the lid and inspected the light leak. As I moved around, I realized that from the table level, almost no light came in but at eye level it was plainly visible.
If you have a makeshift darkroom that can't be dark at high noon, you might have to work at night. If you did a good job darkening, you won't see anything except maybe the green glow of a timer or thermometer when you turn off the light switch. Then after your eyes get accustomed to the light, you may see where light gets in.
Moral of the story... A little light is inevitable...