AZCL, if the center caps remove like my Ram dually, you mentioned a slot. Ours also has a slot between the wheel and cap, with the slot being on the cap. Under our passenger seat is the tool kit and jack for changing a tire. There is a straight steel square bar that is about a foot long with a hook on one, just an "L" bent to a 90 degree angle. You really can't grab the square bar , or I can't, to pull the cap off because more often than not it just jumps out of the slot or if it pulls the cap off, you can easily end up on your butt. What I have been doing is putting a vise grip on the outer end of the bar and hit the vise grips with a dead blow hammer. Has been working every time since I started to do it that way. My vocabulary has sure been better!