When building your kit, you will, at some point, need to remove plastic parts from their ‘trees’. There are many ways to do this, but the preferred way is to carefully cut the parts off with a sharp pair of sidecutters (or scissors).
Once removed, you may see a little bit of plastic left over. This is known as flashing. This ‘gate’ (the technical term for where the plastic flows into the part) needs to be trimmed completely off. Failure to do so could hinder the movement of some of your parts.
It’s a good idea to get into the habit of ‘cleaning’ off all of your parts when building a kit. This will help minimize any handling problems your car might have.