Watch the String!
When you pull the crossbow's trigger, the crossbow string moves forward, following the top of the deck. If your fingers are anywhere in the path of that string, you could get severely injured. When holding the crossbow in the fire position, make absolutely sure that your fingers are NOT above the deck.
This is also an issue for your arms or other parts of your body. When the crossbow is cocked, even if the safety is on and your finger is nowhere near the trigger, don't risk having anything between the string and limbs. Never carry your crossbow by putting your arm between the string and limb.
IMPORTANT! Never dry fire a crossbow. Pulling the trigger when there is no bolt on the deck will cause damage to the crossbow and could cause personal injury.