Autotile Pillars and Platforms


Hi everybody, completely new person to GMS and honestly little more than a novice programmer here!

I'm trying to find a way to make platforms and columns that can be stretched into variable lengths and widths. If I were to just stretch out a sprite in the room editor, it stretches the entire thing, which distorts the image. So I'm trying to use the autotile feature, in order to just draw out whatever pillars and platforms I need into the length and width I need them to individually be.
In doing so, I drew out a 32x64 pillar sprite (leaving space for the first empty tile that I know the autotiler needs), and created a tile set that divided the image up into 7, 32x8 sprites. I then attempted to use the built-in 16 sprite template such that it only uses sprites only for tiles that are attached above, below, or both. However, the autotiler is not accepting this, and merely turns red.

I am guessing that I either am using the incorrect tiles (I can't decipher the format images, and the explanation on the documentation was completely unenlightening in this regard), or that what I am attempting to do is completely impossible. And even if it is, I could very well be going about this in a completely ridiculous manner. If any of you know of either a solution to the autotiler or a more correct and proper way to create variable-length platforms and pillars, please let me know!

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