This is yet another towel holder. I wanted one for some time as I was done with using these crocodile adapters and hooks from the 80th. 
I searched a little to find some matching idea, which would work for me, but sadly there wasn’t a single one. The available models where too big or simply clip together types. The later are odd, as towels are in touch with water and the inside of these little boxes over time gets an bacteria growing place. The given models were click in and the locking mechanism would break over time due to wear off when opening them to clean the inside.
So I used the need and turned it into yet another small FreeCAD session to learn more about CAD. It turned out well and worked first try. 
Printing
Printing is straight forward. There is no support required as the part was designed with build in supports where needed. In fact only the small ring overhang on the cover part would need support anyway. Print the files as they are and you are fine. 0.2mm layer height is fine.
The gripper ring needs to be printed in TPU. Infill should not matter. I used three outside walls, so the object is more or less 100% anyway.
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Assembly
This thingy contains three parts. The base can be screwed to a surface or be taped on, using some good quality double side tape on the back. The gripper object needs to be printed in TPU. It gets sandwiched to the base using the cover, which gets screwed onto the base. The flat side of the TPU ring faces toward the base.
[ATTACH=JSON]{“alt”:“Klicke auf die Grafik f\u00fcr eine vergr\u00f6\u00dferte Ansicht Name: TowelHolder_5.jpg Ansichten: 0 Gr\u00f6\u00dfe: 246,1 KB ID: 9593”,“data-align”:“none”,“data-attachmentid”:“9593”,“data-size”:“medium”}[/ATTACH] [ATTACH=JSON]{“alt”:“Klicke auf die Grafik f\u00fcr eine vergr\u00f6\u00dferte Ansicht Name: TowelHolder_6.jpg Ansichten: 0 Gr\u00f6\u00dfe: 246,3 KB ID: 9594”,“data-align”:“none”,“data-attachmentid”:“9594”,“data-size”:“medium”}[/ATTACH] [ATTACH=JSON]{“alt”:“Klicke auf die Grafik f\u00fcr eine vergr\u00f6\u00dferte Ansicht Name: TowelHolder_7.jpg Ansichten: 0 Gr\u00f6\u00dfe: 250,6 KB ID: 9595”,“data-align”:“none”,“data-attachmentid”:“9595”,“data-size”:“medium”}[/ATTACH]
Thats all. Push a towel into the opening and it will stick. I made it for my
kitchen.
[ATTACH=JSON]{“alt”:“Klicke auf die Grafik f\u00fcr eine vergr\u00f6\u00dferte Ansicht Name: TowelHolder_8.jpg Ansichten: 0 Gr\u00f6\u00dfe: 306,8 KB ID: 9598”,“data-align”:“none”,“data-attachmentid”:“9598”,“data-size”:“medium”}[/ATTACH] [ATTACH=JSON]{“alt”:“Klicke auf die Grafik f\u00fcr eine vergr\u00f6\u00dferte Ansicht Name: TowelHolder_9.jpg Ansichten: 0 Gr\u00f6\u00dfe: 155,9 KB ID: 9596”,“data-align”:“none”,“data-attachmentid”:“9596”,“data-size”:“medium”}[/ATTACH] [ATTACH=JSON]{“alt”:“Klicke auf die Grafik f\u00fcr eine vergr\u00f6\u00dferte Ansicht Name: TowelHolder_10.jpg Ansichten: 0 Gr\u00f6\u00dfe: 168,4 KB ID: 9597”,“data-align”:“none”,“data-attachmentid”:“9597”,“data-size”:“medium”}[/ATTACH]
Modification
If you need a bigger version, load the included source file into FreeCAD and
double click the spreadsheet. I marked the key diameter and height of the box.
Changing other stuff should not be necessary. After that you need to export all
three files and done.
Here is the FreeCAD source file: TowelHolder.FCStd
TowelHolder.FCStd (908 KB)