What is the stiffest?

[Derbyboy]

Biltema's square tube 20x20, thickness 1.5mm

https://www.biltema.se/bygg/byggbes...MIzcinj-jC9wIVZYxoCR0Yngb_EAQYAiABEgKBEvD_BwE

or

Biltema's Angle profile 20x20, thickness 3mm

https://www.biltema.se/bygg/byggbeslag/vinkelprofil/vinkelprofil-2000043584


I will screw it to the ceiling over the råspont where I made a hole for the fan belt.

 

[andersmc]

Biltema's square tube 20x20, thickness 1.5mm

[link]

or

Biltema's Angle Profile 20x20, thickness 3mm

[link]


I will fasten it over the tongue and groove boards in the ceiling where I made a hole for the fan belt.

If by "stiffest" you mean the one with the least deflection under a given load, it's the square tube.

 

[Derbyboy]

Thank you!

I think it's stiffness I'm referring to.

Between the roof joists, there's råspont. The råspont has been cut (230) mm and I want to apply something made of steel there so that the hole does not affect how much the råspont can support.