They can be challenging to start into the hole.
If you have a 5/16 (IIRC) rod or even the shank end of a 5/16 drill, you can align the toggle to the opening in the casting.....then gently move the brake rod end into position and carefully thread it in. Don't cross-thread! If it doesn't readily go in, retry.
Remember to hold your extended tongue at just the right angle, too.