I have the sumo version of a caterham and as such there is a little more room for the tool tubes than I guess some other owners may have. The first one was installed at the end of the drivers footwell, this was put in at a slight angle to allow the top to unscrew easily. The second one went under the crossbracing above the steering column. The second one couldn't go above the crossbracing as that is where I strap the jack and wheel brace.
The first tube installed.
The M8 bolts inside the drivers footwell.
Three 19mm P Clips with 25mm M6 Bolts fix the tube to the underside of the crossbracing.
I also put a tie wrap around the tube and the diagonal to stop the tube rocking side to side and banging on the diagonal.
Two P Clips for the top end of the tool tube.
This shows the jack on top of the crossbracing.
I may change this set up and add a piece of metal to the tool tube to stop the plastic from bending.