1. Click >Resources  >Create Sprite.
2. Click Edit Sprite.
3. Remove the checkmark next to precise collision checking. 
4. Click  >Transform  >Stretch. 
5. Change the pixel size to 16. 
6. Double click the image to draw on it.
7. Zoom into it so you can see it well. 
8. Draw a line down the middle. 
9. Zoomed out the sprite looks like this. 
10. Click the green checkmark. 
11. Click the green checkmark again. 
12. Click Ok.

1. Create Object.
2. Set the Sprite to be the ladder.
3. Do not make it solid.

1. Open up Object Person. 
2. Go to the Step Event. 

This is going to remove the gravity so we can climb the ladder.

1. Drag this action over. 
2. Make these settings to the action. 
3. Drag this beginning of block action.. 
4. Drag this action.    Gravity and Direction are set as 0.
5. Drag the Vertical speed over.    Set as 0.
6. Now the end of block action. 
7. Your step event should now look like this. 

1. Go to your up event. 
2. Drag the Check Object over. 
3. Make these changes. 
4. Drag the Start Block Over. 
5. Drag the Check Empty over. 
6. Set these numbers up and make it relative. 
7. Drag the Jump to the Position action over. 
8. Make these changes to the jump. 

This is really easy.

1. Add a new event for keyboard down. 
2. Go to your keyboard up event. 
3. Hold the shift key and click these 5 actions. 
4. Place your mouse on top of one of these actions.
5. Right Click.
6. Click Copy.
7. Go back to your keyboard down event.
8. 
9. Click once in the empty actions window.
10. Right Click.
11. Click Paste.
12. Your down actions should now look like this. 

Your down key should now work.

   Here is a small example.