All muscles are designed to pull. It's a basic law of human anatomy that every muscle in our bodies are capable of working just one way, and that's by pulling.
The muscle-tendon unit can actively only shorten or contract. That means no matter what action you're getting your body to accomplish, it's some combination of pulling forces that's allowing it to happen.
Let that sink in for a minute.
Hold out your hand. Now close your fingers in to make a fist. It was a combination of several muscles all pulling together to make that happen. Now spread your fingers back out. An entirely different set of muscles all pulled together to allow that to happen.
It's a tough concept to accept. When my teacher first told me that, I spent the next 5 minutes trying to prove her wrong. I moved my arms, waved my legs and in general tried every combination of movement I could think of to show her that there are muscles capable of pushing.
All I succeeded in doing was making the people around me believe I was going into an epileptic fit.
What that means for your workouts is this. Any exercise you're trying to accomplish is only possible through various muscles pulling together. Knowing that, and paying attention to how you position your body to maximize that pulling action can make all the difference between an effective workout and one where you risk injury.