Love it or loathe it, the Smith Machine is a weight room staple. Its fans appreciate that they can use the piece of equipment for squats and bench presses when they don’t have anyone around to spot them. (Since the Smith Machine features a barbell attached to a fixed rail system, solo lifters don’t have to worry about dropping big-time weight on themselves.)

While you can definitely move some serious weight on the Smith Machine, the piece of equipment is also popular with those who are new to lifting because the set movement pattern takes balance and stability out of the lifting equation. This is exactly why some trainers aren’t crazy about the Smith Machine, though. It limits lifters to a straight up-and-down range of motion, which isn’t consistent with how we move in our daily lives. And, working on balance and stability is important!

Still, the Smith Machine is certainly safer for heavy lifting than a solo attempt at free weights, in which case you risk dropping the bar on yourself or others, says personal trainer Kristen Hislop, C.P.T., owner of Hislop Coaching. 

Clearly, opinions on this popular machine are a mixed bag. To get the most out of it (and avoid any mishaps or rookie moves), keep these trainer-backed Smith Machine do’s and don’ts in mind.

• ABOUT OUR EXPERTS: Kristen Hislop, C.P.T., is a certified personal trainer and USA Triathlon coach, as well as the owner of Hislop Coaching. Tyler Read, C.P.T., is a certified personal trainer and the founder of PT Pioneer. TJ Mentus, C.P.T., is a certified personal trainer and a fitness expert with Garage Gym Reviews

Do: Set The Safety Pins 

Setting the pins before you lift is the golden rule of using the Smith Machine. These pins prevent the bar from coming down on you, which could lead to serious injuries, explains personal trainer TJ Mentus, C.P.T., a fitness expert with Garage Gym Reviews. After all, “because the bar is on a track, there is nowhere for it to go but down if you lose your grip on it,” he says. 

Read More: The Top 4 Reasons People Get Injured Working Out

The safety pins stop the weight from falling past a certain point. When setting them, position them to be just below the lowest point the bar will travel for whatever exercise you’re performing, he explains.

Don’t: Make It A Go-To For Bench Presses, Squats, or Shoulder Exercises

In a pinch, you may find yourself using the Smith Machine for some of these classic compound movements, and that’s no biggie. Generally, though, it shouldn’t be your go-to—especially once your form is solid on key exercises like squats.

“When you have good movement patterns, you want to build weight and work on your balance,” says Hislop. “Using the Smith Machine doesn’t allow you to work stabilizing muscles during your lifts.” Since these stabilizing muscles help lifts you do in the gym translate to real-life strength gains, you don’t want to miss out on them. (FYI: research shows that lifters use more muscles during free weight squats than those done on Smith Machines.) 

The Smith Machine also isn’t ideal for bench pressing because it doesn’t detect differences in strength between your two sides, which means your stronger arm will end up dominating, Hislop adds. Incorporating dumbbell bench presses into your routine is a must-do for maintaining muscle balance.

On another note, though many people use the Smith Machine for overhead presses, it’s not an optimal choice, says Hislop. You see, the machine forces a particular plane of motion; instead of moving completely vertically, the bar moves at a seven- to 12-degree angle. This could put you at risk of shoulder injury by essentially forcing an unnatural range of motion.

Do: Use It for Inverted Rows, Hip Thrusts, and Calf Raises

Trainers may not recommend using the Smith Machine for most of your foundational lifts, but it’s actually perfect for a few accessory exercises most strength trainers do. 

One: the inverted row, a bodyweight exercise that’s great for athletes working to progress their other rowing movements. The machine helps protect the back in athletes who may be too rounded in a bent-over row position, she says. 

Read More: Can’t Do Pullups? These Moves Will Get You There

Another great move: hip thrusts. “Often, people will load up a bar too much and use dumbbells that are too heavy when setting up the hip thrust,” she says. “By using a Smith Machine, they can get into position safely without twisting to load weights onto their hips.”

The Smith Machine is also a good option for performing calf raises, because you can often do heavier raises than you’d be able to by holding a free bar or dumbbells on your shoulders, Hislop adds. Boulder calves, here you come.

Do: Use Proper Form

Even though the Smith Machine provides added stability, it’s still important to practice proper form, says personal trainer Tyler Read, C.P.T., the founder of PT Pioneer. Due to its fixed path, there’s a risk of moving in a way that’s not biomechanically natural when using the Smith Machine, which could lead to strain or injury.

“Always make that your joints are aligned correctly, and avoid locking them out during exercises,” he says.

If you choose to use the Smith Machine for squats or lunges, keep your torso upright and in line with the bar, perpendicular to the ground, Mentus notes. This positions the knees to form 90-degree angles when they bend, which is important for proper form and really isolates those lower-body muscles. You’ll also want to make sure your knees track over your toes, adds Read.

Don’t: Use the BOSU Ball with It

A common move that makes trainers cringe: Exercisers using the BOSU ball (a balance trainer that looks like a bouncy ball that’s been cut in half) while training on the Smith Machine. 

“I’ve seen people do this in the gym or post videos online trying to be creative, but these exercises are ineffective and can be dangerous,” Mentus says. “The purpose of the BOSU ball is to provide instability and the Smith Machine completely stabilizes the bar meaning it can’t move with you as you try to balance.” Put simply: It’s a pretty counterintuitive move.

Leave the BOSU ball to your mountain climbers. When used with the Smith Machine, it increases your chances of losing control of the weight and falling, says Mentus.