A securable place is one where, at those inevitable less secure times in every city's future, the most vulnerable parts of the urbanism (like the middle of the block) can be secured, leaving the streets open for everyone to travel there. A securable place is also designed in such a way that it encourages citizens to come outdoors into the public realm, making it safer.
Lining the Street
The best first step to creating a secureable block is inviting the buildings to pull up to the street like in this pedestrian street at Alys Beach. The closer buildings are to the street, the easier it is for its occupants to keep an eye on what's going on outside. And if they sit side-by-side like this, then the courtyards are completely secure and the alley in the center of the block is easily securable if necessary.
The Role of Civic Spaces
Well-designed civic spaces such as plazas, squares (like this one at Alys Beach), greens, and parks entice people outdoors. And a busy street is a far safer place than a deserted one. Civic spaces don't have to be huge. This square is less than one hundred feet across, for example.