what for the building materials will be used under hamas regime in your opinion?
I imagine they will be used for a variety of building projects, some of which may well include bunkers. That in itself is no problem, since bunkers by themselves do not threaten Israel. A bunker is a defensive building, not an offensive weapon.
The blockade imposes idiotic restrictions on what will and will not be allowed into Gaza. Consider the following:
sage
cardamom
cumin
coriander
ginger
jam
halva
vinegar
nutmeg
chocolate
fruit preserves
seeds and nuts
biscuits and sweets
potato chips
gas for soft drinks
dried fruit
fresh meat
plaster
tar
wood for construction
cement
iron
glucose
industrial salt
plastic/glass/metal containers
industrial margarine
tarpaulin sheets for huts
fabric (for clothing)
flavor and smell enhancers
fishing rods
various fishing nets
buoys
ropes for fishing
nylon nets for greenhouses
hatcheries and spare parts for hatcheries
spare parts for tractors
irrigation pipe systems
planters for saplings
heaters for chicken farms
musical instruments
size A4 paper
writing implements
notebooks
newspapers
toys
razors
sewing machines and spare parts
heaters
horses
donkeys
goats
cattle
There is no sane military reason for stopping any of those items from moving into or out of Gaza, so why are they being stopped?
I mean I can understand the rationale for banning coriander. That makes sense. After all, if you get a big enough pile of coriander together then that sucker is going to be bombproof and terrorists might hide under it, right? We wouldn't want Hamas stockpiling coriander for military purposes.
Note that just because I think there is more to this boarding incident than some other people think that does not mean that I think any and all Israeli policies are just dandy. If you want to have a blockade to safeguard your security that's fine but it should be restricted to safeguarding your security, not just banning any old thing for the hell of it. That's just stupid and will only increase the number of your enemies.
As a result of this debacle Turkey is talking about giving future ships a naval escort. I think what really should happen is that they get a NATO escort. That would reduce the chances of things escalating since the other countries could keep the Turks a bit cooler and since Israel is not going to attack NATO escorts. The ships could be loaded under NATO supervision so that Israel has no reason to fear they will be carrying smuggled weapons. NATO supervision would also mean idiots who want to be martyred and possibly cause the deaths of other people could be screened out before the ships leave port.