About this 3D model

I want to make something simple... I know rollers can be used and do a better job... but I want to make this full 3d printed... The idea is to have a little base that you can hang in the border of your spools holder... as I don't have any meansurement of your place, take this as a idea only!!!The idea is to have a base with rails, so you can put the rollers on the perfect position depending on the size of the spool... I know the bed needs to hold a loot of weight for a loot of time, but as I don't know the size of the woods, how deep is the border, etc... this is the best I can do...I was thinking on a screwed press on the bottom part of the base... but I'm really new on 123D and its a little difficult to do screws on it...