Continuity mistake: Right at the start, when the woman says, "Why can't you be more like your brother?" the cereal the kid has changes position/amount between shots. (00:02:10)
Continuity mistake: When Paige walks out to Blake in his car he kisses her. When it cuts his hand is suddenly on her chin. (00:04:55)
Continuity mistake: When Nick is having the conversation about stealing the car, he has a lighter against a beer bottle. When it cuts the lighter is out, and nowhere near as close to the bottle as it was. (00:13:20)
Continuity mistake: When Carly has fallen into the road kill pit, the amount of dirt on her hands keeps changing instantly. (00:20:50)
Continuity mistake: When the weird man gives Carly and Wade a ride, he steps out of the car to let them out. However, he does this twice in different shots. (00:26:30)
Continuity mistake: When Carly wipes the mirror and sees the person in the window, the area of wiped glass on the mirror alternates between two different versions. (00:36:30)
Continuity mistake: When Carly wipes the dust off the mirror in the wax museum, the initial double hand swipe is repeated in the next shot. (00:38:00)
Continuity mistake: When Carly locks herself in the truck, the owner throws to the ground the box holding the fan belt and a few other things, right beside the driver's side of the truck. In the next exterior shot, there is nothing on the ground. (00:50:50)
Continuity mistake: At the beginning of the scene when Paige and Blake are alone in the tent, there is a shot of Blake's cell phone sat atop a CD case, with the top line of the display showing the date and time and "NewVoiceMessage" below it. When the music stops and Blake runs out of the tent, the phone is seen in a different orientation on the CD case but still has the date/time as the top line. After Blake restarts the music, he then picks the phone up, which is still in its new position but no longer has the date/time displayed on the top line. (01:08:10 - 01:09:45)
Continuity mistake: After Vincent has stabbed Blake in the neck at the campsite, a terrified Paige runs for her life and tries to hide in a large dark building (the abandoned sugar mill). Whilst she is running through dark hallways, she passes through patches of moonlight and we see that her eyes are dry, and her face doesn't exactly show an expression of terror (Hilton's poor acting perhaps?). However, seconds later, she crouches down to hide and the lights are turned on, and we see that she is crying and tears are streamed across her face, yet she was not sobbing nor crying before she crouched down, merely screaming and panting. Immediately afterwards, when she is searching through a box of discarded cellphones, her face is once again dry and her eyes not red, and it remains dry throughout the rest of the scene, despite her not having wiped her face at all (including the scene of her face right before Vincent impales her: her mascara is completely untouched). (01:11:20 - 01:11:50)
Continuity mistake: After having shot Bo with a stolen crossbow, Carly and Nick search the Sinclair house for help. When Carly comes across a drawer filled with newspaper clippings and childhood photographs of the Sinclair brothers, Bo and Vincent are seen on these photos as having very fair, almost light brown hair, and yet in the film, the adult brothers both have very dark black hair. It is possible that they could have dyed it in the past, but considering one is a deranged psychopathic killer and the other his simple-minded disfigured sidekick, this seems very unlikely (admittedly, hair color can grow darker over the years, but not the the extent of changing color completely, and the photos of Bo and Vincent show them around 5 or 6 years old, not toddlers). (01:23:15)
Continuity mistake: As we see Vincent falling through the wax floor, the depth that he has sunk in changes between shots. (01:25:20)
Continuity mistake: Nick's shirt he gave to Carly is way too big on her when she first puts it on. In the next scene it fits like it's her own shirt.
Continuity mistake: When Paige is 'spiked' by Vincent, she falls onto her hands and knees and her hands are in fists. Yet after Vincent starts filming her they have changed.
Continuity mistake: Elisha Cuthbert is a foot shorter than Jared Padalecki, so they stacked blocks under her shoes to make her appear taller (as seen in one of the extras). However, in full body shots there is nothing under her feet and she's much shorter than those shots when you can't see her feet.
Continuity mistake: When Carly is in the wax bedroom near the end of the film, she is fending off Vincent with a bat. She lays the bat on the wax bed while talking, and it leaves an imprint in the wax. When she runs on the bed to the other side, the imprint is gone.
Continuity mistake: When Carly is taken into the basement under the gas station, her kidnapper turns the radio on when they enter the room and he locks the door when he leaves, leaving the radio on. When Nick runs inside the gas station, the door is unlocked and the radio is off.
Continuity mistake: When Carly, Nick and Bo are walking up against Bo's house, Carly's hands change from being crossed behind her back to hanging down between the shots.
Continuity mistake: When Wade and Carly first enter the church and think they have 'interrupted' the funeral, we see a close up of the priest's face. He looks like a real person just standing very still. Later in the film when there are more prolonged shots of the priest (when Carly hides under his clothes from Bo), you can see he is now a lot more 'waxy' and fake.
Answer: It is simply a contraption to keep Wade in place so he doesn't move and the wax can be applied. It's also used to keep the wax out of his eyes, ears, nose and mouth.