Two guys who apparently didn't know that swords can be deadly weapons learned that one the hard way Friday, after an incident of bladed horseplay sent one man to the hospital and the other to jail.

According to the San Francisco Police Department, the two guys were "hanging out in an apartment together" Friday on the 900 block of Columbus Avenue, which is between Chestnut and Lombard Streets.

At around 10:21 a.m., they started "wrestling/playing with" a sword, police say. In the midst of the tomfoolery, one of the men "ends up with stab wounds," police say.

The victim was transported to San Francisco General Hospital for treatment of injuries police say are not life-threatening. The alleged stabber, a man who at age 40 is certainly old enough to know better, was arrested.

And that, my friends, is why you don't play with swords. Just in case you needed to be reminded.