We have here a 7/8 inch wide trailer coupler latch lock. This is a lock for the latch of your coupler and we are going to show you how it works, it is a pretty simple device. Basically you have the key to unlock it and then we will show you how to install it. It has a nice weather tight cover, you turn the key about 180 degrees and the pin comes apart and it is ready to install on your coupler. We have your regular variety latch style coupler here and we will show you how it works. The lock wraps around, you put the pin in and turn the key, put the cover back on and your trailer is secure. A few finer points about this lock is that the body itself has a nice rubber grip surrounding it which makes it easier to use and grab. You have armor on the outside which is covered in plastic so it will not scratch up your new trailer. It could be important on galvanized trailers because you do not want to beat it up and start rusting and cracking. What is also nice is the key itself. It is not a special key, if you take it to the locksmith you can get a copy made. There you have it for part # 2878DAT, from MasterLock, the 7/8 inch wide coupler latch lock.