I used these T-slot nuts with side approach to mount my power supply mod for the Ender 3 pro to the end of the aluminum profile to make it stiffer. Normally you would use the four holes, but you have to tap thread. If your requirements regarding strength aren’t that high, these things will hold fine. So, don’t use this for constructional purposes.
I haven’t tested the strength thoroughly and I recon that the pull out force can be increased with other print orientations and more abrasive materials e.g. Nylon with carbon fiber. I have printed the ones you see in the picture with PETG which is rather smooth and I am able to pull them out by hand. If these things turn out to be useful for other purposes it would be interesting to dive deeper in increasing its pull-out strength.