Visit trailer-specific websites and buy a ramp that fits your specific trailer. This is likely your safest and most reliable option. You can buy ramps in whatever size you need--from narrow to extra wide--that hook onto your trailer and won't move. Consider the type of trailer you need. For example, some trailer ramps are set up like ladders (best for animals), others are solid and great for dollys and some are a series of bars that are ideal for loading a small vehicle.
Create your own utility trailer ramp with a piece of sturdy wood. This is a handy alternative to a pre-made product, especially if you already have wood on hand. A wide and sturdy piece is best, but if you only have thin pieces of wood, you can screw them together to create a sturdier foundation. If your wood isn't wide enough, use a cross section of wood or a piece of metal to fasten the pieces together.
If you have a thick piece of sheet metal hanging around, this is a perfect option. Because it's metal, it shouldn't give in under a lot of pressure. Secure the metal piece onto the lip of the trailer. You can do this by adhering thick, metal hooks to the top of the metal sheet that you can latch onto the trailer.
