Given a set of age nodes \(0=x_0,x_1,\ldots,x_n\) and survival fractions \(1=\sfrac(x_0),\sfrac(x_1),\dots,\sfrac(x_n)\) the force of mortality over the interval \([x_i,x_{i+1})\) is a constant spread \(\spread_i\) relative to a standard curve \(\ssfrac(x)\). \begin{equation} \sfrac(x)=\sfrac(x_i) \left(\frac{\ssfrac(x)}{\ssfrac(x_i)}\right) e^{-\spread_i (x-x_i)},\quad x\in [x_i,x_{i+1}) \end{equation} The build method property must be of the form ABS_SPREAD:SMortHandle where SMortHandle is the name of the standard mortality object enclosed in quotes.